NAME
       ksh,  rksh,  pfksh  - KornShell, a standard/restricted command and pro-
       gramming language

SYNOPSIS
       ksh [ ?abcefhiknoprstuvxBCDP ] [ -R file ] [ ?o option ] ... [  -  ]  [
       arg ... ]

DESCRIPTION
       Ksh  is  a command and programming language that executes commands read
       from a terminal or a file.  Rksh is a restricted version of the command
       interpreter  ksh;  it is used to set up login names and execution envi-
       ronments whose capabilities are more controlled than those of the stan-
       dard  shell.   Rpfksh  is a profile shell version of the command inter-
       preter ksh; it is used to to execute commands with the attributes spec-
       ified by the user's profiles (see pfexec(1)).  See Invocation below for
       the meaning of arguments to the shell.

       NOTE: Pfksh, Rpfksh and pfexec parts are not related to Linux  systems.
       Rksh can be used as rksh symlink to ksh93 or as ksh -r.

   Definitions.
       A metacharacter is one of the following characters:

              ;   &   (   )   |   <   >   new-line   space   tab

       A  blank  is a tab or a space.  An identifier is a sequence of letters,
       digits, or underscores starting with a letter or  underscore.   Identi-
       fiers  are used as components of variable names.  A vname is a sequence
       of one or more identifiers separated by a . and optionally preceded  by
       a  ..   Vnames  are  used  as function and variable names.  A word is a
       sequence of characters from the character set defined  by  the  current
       locale, excluding non-quoted metacharacters.

       A  command  is a sequence of characters in the syntax of the shell lan-
       guage.  The shell reads each command and carries out the desired action
       either  directly or by invoking separate utilities.  A built-in command
       is a command that is carried out by the shell itself without creating a
       separate  process.   Some  commands are built-in purely for convenience
       and are not documented here.  Built-ins that cause side effects in  the
       shell environment and built-ins that are found before performing a path
       search (see Execution below) are documented here.  For historical  rea-
       sons,  some  of these built-ins behave differently than other built-ins
       and are called special built-ins.

   Commands.
       A simple-command is  a  list  of  variable  assignments  (see  Variable
       Assignments  below) or a sequence of blank separated words which may be
       preceded by a list of variable  assignments  (see  Environment  below).
       The  first  word  specifies  the  name  of  the command to be executed.
       Except as specified below, the remaining words are passed as  arguments
       to  the invoked command.  The command name is passed as argument 0 (see
       exec(2)).  The value of a simple-command is its exit status;  0-255  if
       it  terminates  normally;  256+signum  if it terminates abnormally (the
       name of the signal corresponding to the exit status can be obtained via
       the -l option of the kill built-in utility).

       A  pipeline  is a sequence of one or more commands separated by |.  The
       standard output of each command but the last is connected by a  pipe(2)
       to the standard input of the next command.  Each command, except possi-
       bly the last, is run as a separate process; the  shell  waits  for  the
       last  command  to terminate.  The exit status of a pipeline is the exit
       status of the last command unless the pipefail option is enabled.  Each
       pipeline  can be preceded by the reserved word !  which causes the exit
       status of the pipeline to become 0 if the exit status of the last  com-
       mand is non-zero, and 1 if the exit status of the last command is 0.

       A  list  is  a sequence of one or more pipelines separated by ;, &, |&,
       &&, or ||, and optionally terminated by ;, &, or  |&.   Of  these  five
       symbols,  ;,  &, and |& have equal precedence, which is lower than that
       of && and ||.  The symbols && and || also  have  equal  precedence.   A
       semicolon (;) causes sequential execution of the preceding pipeline; an
       ampersand (&) causes asynchronous execution of the  preceding  pipeline
       (i.e.,  the shell does not wait for that pipeline to finish).  The sym-
       bol |& causes asynchronous execution of the preceding pipeline  with  a
       two-way  pipe  established  to the parent shell; the standard input and
       output of the spawned pipeline can be written to and read from  by  the
       parent shell by applying the redirection operators <& and >& with arg p
       to commands and by using -p option of the built-in  commands  read  and
       print described later.  The symbol && (||) causes the list following it
       to be executed only if the preceding pipeline returns a zero (non-zero)
       value.   One  or more new-lines may appear in a list instead of a semi-
       colon, to delimit a command.  The first item  of the first pipeline  of
       a  list  that is a simple command not beginning with a redirection, and
       not occurring within a while, until, or if list, can be preceded  by  a
       semicolon.   This  semicolon  is  ignored  unless  the showme option is
       enabled as described with the set built-in below.

       A command is either a simple-command or one of the  following.   Unless
       otherwise  stated,  the value returned by a command is that of the last
       simple-command executed in the command.

       for vname [ in word ... ] ;do list ;done
              Each time a for command is executed, vname is set  to  the  next
              word  taken  from the in word list.  If in word ...  is omitted,
              then the for command executes the do list once  for  each  posi-
              tional  parameter  that  is  set  starting from 1 (see Parameter
              Expansion below).  Execution ends when there are no  more  words
              in the list.

       for (( [expr1] ; [expr2] ; [expr3] )) ;do list ;done
              The  arithmetic  expression expr1 is evaluated first (see Arith-
              metic evaluation below).  The  arithmetic  expression  expr2  is
              repeatedly  evaluated  until  it evaluates to zero and when non-
              zero, list is executed and the arithmetic expression expr3 eval-
              uated.   If  any expression is omitted, then it behaves as if it
              evaluated to 1.

       select vname [ in word ... ] ;do list ;done
              A select command prints on standard error  (file  descriptor  2)
              the set of words, each preceded by a number.  If in word ...  is
              omitted, then the positional parameters starting from 1 are used
              instead  (see  Parameter  Expansion  below).   The PS3 prompt is
              printed and a line is read from the  standard  input.   If  this
              line consists of the number of one of the listed words, then the
              value of the variable vname is set to the word corresponding  to
              this  number.   If  this  line  is  empty, the selection list is
              printed again.  Otherwise the value of the variable vname is set
              to  null.   The contents of the line read from standard input is
              saved in the variable REPLY.  The  list  is  executed  for  each
              selection  until  a break or end-of-file is encountered.  If the
              REPLY variable is set to null by the execution of list, then the
              selection  list  is printed before displaying the PS3 prompt for
              the next selection.

       case word in [ [(]pattern [ | pattern ] ... ) list ;; ] ... esac
              A case command executes the list associated with the first  pat-
              tern that matches word.  The form of the patterns is the same as
              that used for file-name generation  (see  File  Name  Generation
              below).   The ;; operator causes execution of case to terminate.
              If ;& is used in place of ;; the next subsequent list,  if  any,
              is executed.

       if list ;then list [ ;elif list ;then list ] ... [ ;else list ] ;fi
              The list following if is executed and, if it returns a zero exit
              status, the list following the first then is  executed.   Other-
              wise,  the  list following elif is executed and, if its value is
              zero, the list following the next  then  is  executed.   Failing
              each successive elif list, the else list is executed.  If the if
              list has non-zero exit status and there is no  else  list,  then
              the if command returns a zero exit status.

       while list ;do list ;done
       until list ;do list ;done
              A  while  command repeatedly executes the while list and, if the
              exit status of the last command in the list  is  zero,  executes
              the  do  list; otherwise the loop terminates.  If no commands in
              the do list are executed, then the while command returns a  zero
              exit  status;  until may be used in place of while to negate the
              loop termination test.

       ((expression))
              The expression is evaluated using the rules for arithmetic eval-
              uation  described below.  If the value of the arithmetic expres-
              sion is non-zero, the exit status is 0, otherwise the exit  sta-
              tus is 1.

       (list)
              Execute list in a separate environment.  Note, that if two adja-
              cent open parentheses are needed for nesting, a  space  must  be
              inserted  to  avoid  evaluation  as  an  arithmetic  command  as
              described above.

       { list;}
              list is simply executed.  Note that unlike the metacharacters  (
              and  ),  { and } are reserved words and must occur at the begin-
              ning of a line or after a ; in order to be recognized.

       [[ expression ]]
              Evaluates expression and returns a zero exit status when expres-
              sion is true.  See Conditional Expressions below, for a descrip-
              tion of expression.

       function varname { list ;}
       varname () { list ;}
              Define a function which is referenced by  varname.   A  function
              whose  varname contains a .  is called a discipline function and
              the portion of the varname preceding the last .  must  refer  to
              an  existing  variable.  The body of the function is the list of
              commands between { and }.  A function defined with the  function
              varname syntax can also be used as an argument to the .  special
              built-in command to get the equivalent behavior as if  the  var-
              name() syntax were used to define it.  (See Functions below.)

       time [ pipeline ]
              If  pipeline is omitted the user and system time for the current
              shell and completed  child  processes  is  printed  on  standard
              error.   Otherwise, pipeline is executed and the elapsed time as
              well as the user and system time are printed on standard  error.
              The TIMEFORMAT variable may be set to a format string that spec-
              ifies how the timing information should be displayed.  See Shell
              Variables below for a description of the TIMEFORMAT variable.

       The  following reserved words are recognized as reserved only when they
       are the first word of a command and are not quoted:

       if then else elif fi case esac for while until do  done  {  }  function
       select time [[ ]] !

   Variable Assignments.
       One  or  more variable assignments can start a simple command or can be
       arguments to the typeset, enum, export, or  readonly  special  built-in
       commands  as  well  as  to other declaration commands created as types.
       The syntax for an assignment is of the form:

       varname=word
       varname[word]=word
              No space is permitted between varname and the = or between = and
              word.

       varname=(assign_list)
              No space is permitted between varname and the =.  An assign_list
              can be one of the following:
                      word ...
                             Indexed array assignment.
                      [word]=word ...
                             Associative array  assignment.   If  preceded  by
                             typeset  -a  this  will  create  an indexed array
                             instead.
                      assignment ...
                             Compound variable  assignment.   This  creates  a
                             compound  variable  varname with sub-variables of
                             the form varname.name, where  name  is  the  name
                             portion of assignment.  The value of varname will
                             contain all the assignment elements.   Additional
                             assignments made to sub-variables of varname will
                             also be displayed as part of the  value  of  var-
                             name.   If  no assignments are specified, varname
                             will be a compound variable allowing  subsequence
                             child elements to be defined.
                      typeset [options] assignment ...
                             Nested variable assignment.  Multiple assignments
                             can be specified by separating each of them  with
                             a  ;.   The  previous  value  is unset before the
                             assignment.  Other declaration commands  such  as
                             readonly,  enum,  and  other declaration commands
                             can be used in place of typeset.
                      . filename
                             Include  the  assignment  commands  contained  in
                             filename.

       In addition, a += can be used in place of the = to signify adding to or
       appending to the previous value.  When += is applied to  an  arithmetic
       type,  word  is  evaluated as an arithmetic expression and added to the
       current value.  When applied to a string variable, the value defined by
       word  is appended to the value.  For compound assignments, the previous
       value is not unset and the new values are appended to the current  ones
       provided that the types are compatible.

       The  right  hand side of a variable assignment undergoes all the expan-
       sion listed below except word splitting, brace expansion, and file name
       generation.   When  the  left  hand side is an assignment is a compound
       variable and the right hand is the name of  a  compound  variable,  the
       compound  variable  on the right will be copied or appended to the com-
       pound variable on the left.

   Comments.
       A word beginning with # causes that word and all the following  charac-
       ters up to a new-line to be ignored.
   Aliasing.
       The  first  word of each command is replaced by the text of an alias if
       an alias for this word has been defined.  An alias name consists of any
       number of characters excluding metacharacters, quoting characters, file
       expansion characters,  parameter  expansion  and  command  substitution
       characters,  and =.  The replacement string can contain any valid shell
       script including the metacharacters listed above.  The  first  word  of
       each  command in the replaced text, other than any that are in the pro-
       cess of being replaced, will be tested for aliases.  If the last  char-
       acter  of  the alias value is a blank then the word following the alias
       will also be checked for alias substitution.  Aliases can  be  used  to
       redefine  built-in commands but cannot be used to redefine the reserved
       words listed above.  Aliases can be created and listed with  the  alias
       command and can be removed with the unalias command.
       Aliasing  is  performed  when scripts are read, not while they are exe-
       cuted.  Therefore, for an alias to take effect,  the  alias  definition
       command  has  to  be  executed  before the command which references the
       alias is read.
       The following aliases are compiled into the shell but can be  unset  or
       redefined:
                           autoload=?typeset -fu?
                           command=?command  ?
                           compound=?typeset -C?
                           fc=hist
                           float=?typeset -lE?
                           functions=?typeset -f?
                           hash=?alias -t --?
                           history=?hist -l?
                           integer=?typeset -li?
                           nameref=?typeset -n?
                           nohup=?nohup  ?
                           r=?hist -s?
                           redirect=?command exec?
                           source=?command .?
                           stop=?kill -s STOP?
                           suspend=?kill -s STOP $$?
                           times=?{ { time;} 2>&1;}?
                           type=?whence -v?

   Tilde Substitution.
       After  alias  substitution is performed, each word is checked to see if
       it begins with an unquoted ~.  For tilde substitution, word also refers
       to  the  word  portion  of parameter expansion (see Parameter Expansion
       below).  If it does, then the word up to a / is checked to  see  if  it
       matches  a user name in the password database (See getpwname(3).)  If a
       match is found, the ~ and the matched login name are  replaced  by  the
       login  directory of the matched user.  If no match is found, the origi-
       nal text is left unchanged.  A ~ by itself, or in  front  of  a  /,  is
       replaced  by  $HOME.  A ~ followed by a + or - is replaced by the value
       of $PWD and $OLDPWD respectively.

       In addition, when expanding a variable assignment,  tilde  substitution
       is attempted when the value of the assignment begins with a ~, and when
       a ~ appears after a :.  The : also terminates a ~ login name.

   Command Substitution.
       The standard output from a command list enclosed  in  parentheses  pre-
       ceded  by  a dollar sign ( $(list) ), or in a brace group preceded by a
       dollar sign ( ${ list;} ), or in a pair of grave accents  (``)  may  be
       used  as part or all of a word; trailing new-lines are removed.  In the
       second case, the { and } are treated as a reserved words so that { must
       be  followed  by a blank and } must appear at the beginning of the line
       or follow a ;.  In the third (obsolete) form, the  string  between  the
       quotes  is  processed for special quoting characters before the command
       is executed (see Quoting below).  The command substitution $(cat  file)
       can  be  replaced  by  the equivalent but faster $(<file).  The command
       substitution $(n<#) will expand to the current  byte  offset  for  file
       descriptor n.  Except for the second form, the command list is run in a
       subshell so that no side effects are possible.  For  the  second  form,
       the final } will be recognized as a reserved word after any token.

   Arithmetic Substitution.
       An  arithmetic  expression enclosed in double parentheses preceded by a
       dollar sign ( $(()) ) is  replaced  by  the  value  of  the  arithmetic
       expression within the double parentheses.

   Process Substitution.
       This feature is only available on versions of the UNIX operating system
       that support the /dev/fd directory for naming open files.  Each command
       argument  of  the  form  <(list) or >(list) will run process list asyn-
       chronously connected to some file in /dev/fd.  The name  of  this  file
       will  become  the  argument  to  the  command.   If  the form with > is
       selected then writing on this file will provide input for list.   If  <
       is used, then the file passed as an argument will contain the output of
       the list process.  For example,

              paste <(cut -f1 file1) <(cut -f3 file2) | tee >(process1) >(pro-
              cess2)

       cuts fields 1 and 3 from the files file1 and file2 respectively, pastes
       the results together, and sends it to the processes process1  and  pro-
       cess2,  as  well as putting it onto the standard output.  Note that the
       file, which is passed as an argument to the command, is a UNIX  pipe(2)
       so programs that expect to lseek(2) on the file will not work.

       Process  substitution  of  the form <(list) can also be used with the <
       redirection operator which causes the output of  list  to  be  standard
       input or the input for whatever file descriptor is specified.

   Parameter Expansion.
       A parameter is a variable, one or more digits, or any of the characters
       *, @, #, ?, -, $, and !.  A variable is denoted by a vname.  To  create
       a variable whose vname contains a ., a variable whose vname consists of
       everything before the last . must already  exist.   A  variable  has  a
       value  and  zero  or more attributes.  Variables can be assigned values
       and attributes by using the  typeset  special  built-in  command.   The
       attributes  supported by the shell are described later with the typeset
       special  built-in  command.   Exported  variables   pass   values   and
       attributes to the environment.

       The  shell supports both indexed and associative arrays.  An element of
       an array variable is referenced by a subscript.   A  subscript  for  an
       indexed  array  is  denoted by an arithmetic expression (see Arithmetic
       evaluation below) between a [ and a ].  To assign values to an  indexed
       array, use vname=(value ...) or set -A vname  value ... .  The value of
       all  non-negative  subscripts  must  be  in  the  range  of  0  through
       4,194,303.  A negative subscript is treated as an offset from the maxi-
       mum current index +1 so that -1 refers to the  last  element.   Indexed
       arrays  can  be declared with the -a option to typeset.  Indexed arrays
       need not be declared.  Any reference to a variable with  a  valid  sub-
       script is legal and an array will be created if necessary.

       An  associative array is created with the -A option to typeset.  A sub-
       script for an associative array is denoted by a string enclosed between
       [ and ].

       Referencing  any array without a subscript is equivalent to referencing
       the array with subscript 0.

       The value of a variable may be assigned by writing:

              vname=value [ vname=value ] ...

       or
              vname[subscript]=value [ vname[subscript]=value ] ...
       Note that no space is allowed before or after the =.
       A nameref is a variable that is a reference  to  another  variable.   A
       nameref  is created with the -n attribute of typeset.  The value of the
       variable at the time of the typeset command becomes the  variable  that
       will  be referenced whenever the nameref variable is used.  The name of
       a nameref cannot contain a ..  When a variable or  function  name  con-
       tains  a  .,  and the portion of the name up to the first . matches the
       name of a nameref, the variable referred to is  obtained  by  replacing
       the  nameref  portion  with  the name of the variable referenced by the
       nameref.  If a nameref is used as the index of a for loop, a name  ref-
       erence  is established for each item in the list.  A nameref provides a
       convenient way to refer to the variable inside a function whose name is
       passed  as  an  argument  to a function.  For example, if the name of a
       variable is passed as the first argument to a function, the command
              typeset -n var=$1
       inside the function causes references and assignments to var to be ref-
       erences  and  assignments to the variable whose name has been passed to
       the function.
       If any of the floating point attributes, -E, -F, or -X, or the  integer
       attribute,  -i,  is  set for vname, then the value is subject to arith-
       metic evaluation as described below.
       Positional parameters, parameters denoted by a number, may be  assigned
       values with the set special built-in command.  Parameter $0 is set from
       argument zero when the shell is invoked.
       The character $ is used to introduce substitutable parameters.
       ${parameter}
              The shell reads all the characters from ${ to the matching }  as
              part  of the same word even if it contains braces or metacharac-
              ters.  The value, if any, of the parameter is substituted.   The
              braces  are  required  when  parameter  is followed by a letter,
              digit, or underscore that is not to be interpreted  as  part  of
              its  name,  when the variable name contains a ..  The braces are
              also required when a variable is subscripted unless it  is  part
              of  an  Arithmetic  Expression  or a Conditional Expression.  If
              parameter is one or more digits then it is a positional  parame-
              ter.   A  positional  parameter  of  more than one digit must be
              enclosed in braces.  If parameter is * or @, then all the  posi-
              tional  parameters, starting with $1, are substituted (separated
              by a field separator character).  If an array  vname  with  sub-
              script  *  @,  or  of the form sub1 ..  sub2.  is used, then the
              value for each of the elements between sub1 and  sub2  inclusive
              (or  all  elements for * and @) is substituted, separated by the
              first character of the value of IFS.
       ${#parameter}
              If parameter is * or @, the number of positional  parameters  is
              substituted.   Otherwise, the length of the value of the parame-
              ter is substituted.
       ${#vname[*]}
       ${#vname[@]}
              The number of elements in the array vname is substituted.

       ${@vname}
              Expands to  the  type  name  (See  Type  Variables    below)  or
              attributes of the variable referred to by vname.
       ${!vname}
              Expands  to the name of the variable referred to by vname.  This
              will be vname except when vname is a name reference.
       ${!vname[subscript]}
              Expands to name of the subscript unless subscript is *,  @.   or
              of  the  form  sub1  ..  sub2.  When subscript is *, the list of
              array subscripts for vname is generated.  For a variable that is
              not  an array, the value is 0 if the variable is set.  Otherwise
              it is null.  When subscript is @, same  as  above,  except  that
              when  used in double quotes, each array subscript yields a sepa-
              rate argument.  When subscript is of the form sub1 ..   sub2  it
              expands  to  the list of subscripts between sub1 and sub2 inclu-
              sive using the same quoting rules as @.
       ${!prefix*}
              Expands to the names of the variables  whose  names  begin  with
              prefix.
       ${parameter:-word}
              If  parameter  is set and is non-null then substitute its value;
              otherwise substitute word.
       ${parameter:=word}
              If parameter is not set or is null then  set  it  to  word;  the
              value  of the parameter is then substituted.  Positional parame-
              ters may not be assigned to in this way.
       ${parameter:?word}
              If parameter is set and is non-null then substitute  its  value;
              otherwise,  print  word and exit from the shell (if not interac-
              tive).  If word is omitted then a standard message is printed.
       ${parameter:+word}
              If parameter is set and is non-null then substitute word; other-
              wise substitute nothing.
       In the above, word is not evaluated unless it is to be used as the sub-
       stituted string, so that, in the following  example,  pwd  is  executed
       only if d is not set or is null:
              print ${d:-$(pwd)}
       If  the  colon  (  :  ) is omitted from the above expressions, then the
       shell only checks whether parameter is set or not.
       ${parameter:offset:length}
       ${parameter:offset}
              Expands to the portion of the value of parameter starting at the
              character (counting from 0) determined by expanding offset as an
              arithmetic expression and consisting of the number of characters
              determined  by  the arithmetic expression defined by length.  In
              the second form, the remainder of the value is used.  If A nega-
              tive  offset  counts  backwards from the end of parameter.  Note
              that one or more blanks is required in front of a minus sign  to
              prevent  the  shell  from  interpreting  the operator as :-.  If
              parameter is * or @, or is an array name indexed by * or @, then
              offset  and  length  refer to the array index and number of ele-
              ments respectively.  A negative offset is taken relative to  one
              greater  than  the  highest  subscript  for indexed arrays.  The
              order for associate arrays is unspecified.
       ${parameter#pattern}
       ${parameter##pattern}
              If the shell pattern matches  the  beginning  of  the  value  of
              parameter,  then the value of this expansion is the value of the
              parameter with the matched portion deleted; otherwise the  value
              of  this parameter is substituted.  In the first form the small-
              est matching pattern is deleted  and  in  the  second  form  the
              largest matching pattern is deleted.  When parameter is @, *, or
              an array variable with subscript @ or *, the substring operation
              is applied to each element in turn.

       ${parameter%pattern}
       ${parameter%%pattern}
              If  the shell pattern matches the end of the value of parameter,
              then the value of this expansion is the value of  the  parameter
              with the matched part deleted; otherwise substitute the value of
              parameter.  In the first form the smallest matching  pattern  is
              deleted  and  in the second form the largest matching pattern is
              deleted.  When parameter is @, *, or an array variable with sub-
              script  @  or *, the substring operation is applied to each ele-
              ment in turn.

       ${parameter/pattern/string}
       ${parameter//pattern/string}
       ${parameter/#pattern/string}
       ${parameter/%pattern/string}
              Expands parameter and replaces the longest match of pattern with
              the  given  string.  Each occurrence of \n in string is replaced
              by the portion of parameter that matches the  n-th  sub-pattern.
              In  the  first  form,  only  the  first occurrence of pattern is
              replaced.  In  the  second  form,  each  match  for  pattern  is
              replaced by the given string.  The third form restricts the pat-
              tern match to the beginning of the string while the fourth  form
              restricts  the  pattern  match  to  the end of the string.  When
              string is null, the pattern will be deleted and the /  in  front
              of  string  may be omitted.  When parameter is @, *, or an array
              variable with subscript @ or *, the  substitution  operation  is
              applied  to each element in turn.  In this case, the string por-
              tion of word will be re-evaluated for each element.

       The following parameters are automatically set by the shell:
              #      The number of positional parameters in decimal.
              -      Options supplied to the shell on invocation or by the set
                     command.
              ?      The  decimal value returned by the last executed command.
              $      The process number of this shell.
              _      Initially, the value of _ is an absolute pathname of  the
                     shell  or script being executed as passed in the environ-
                     ment.  Subsequently it is assigned the last  argument  of
                     the previous command.  This parameter is not set for com-
                     mands which are asynchronous.   This  parameter  is  also
                     used  to  hold  the  name  of the matching MAIL file when
                     checking for mail.  While defining a compound variable or
                     a  type,  _ is initialized as a reference to the compound
                     variable or type.  When a discipline function is invoked,
                     _  is  initialized as a reference to the variable associ-
                     ated with the call to this function.  Finally when  _  is
                     used  as the name of the first variable of a type defini-
                     tion, the new type is derived from the type of the  first
                     variable (See Type Variables  below.).
              !      The process number of the last background command invoked
                     or the most recent job put in the background with the  bg
                     built-in command.
              .sh.command
                     When  processing a DEBUG trap, this variable contains the
                     current command line that is about to run.
              .sh.edchar
                     This variable contains the value of the keyboard  charac-
                     ter  (or sequence of characters if the first character is
                     an ESC, ascii 033) that has been entered when  processing
                     a  KEYBD  trap (see Key Bindings below).  If the value is
                     changed as part of the trap action, then  the  new  value
                     replaces  the key (or key sequence) that caused the trap.
              .sh.edcol
                     The character position of the cursor at the time  of  the
                     most recent KEYBD trap.
              .sh.edmode
                     The  value  is  set  to  ESC when processing a KEYBD trap
                     while in vi insert mode.  (See Vi Editing Mode    below.)
                     Otherwise,  .sh.edmode  is  null  when processing a KEYBD
                     trap.
              .sh.edtext
                     The characters in the input buffer at  the  time  of  the
                     most  recent KEYBD trap.  The value is null when not pro-
                     cessing a KEYBD trap.
              .sh.file
                     The pathname of the file than contains the  current  com-
                     mand.
              .sh.fun
                     The  name of the current function that is being executed.
              .sh.level
                     Set to the current function depth.  This can  be  changed
                     inside a DEBUG trap and will set the context to the spec-
                     ified level.
              .sh.lineno
                     Set during a DEBUG trap to the line number for the caller
                     of each function.
              .sh.match
                     An  indexed  array which stores the most recent match and
                     sub-pattern matches  after  conditional  pattern  matches
                     that match and after variables expansions using the oper-
                     ators #, %, or /.  The 0-th element stores  the  complete
                     match  and  the  i-th.  element stores the i-th submatch.
                     The .sh.match variable becomes unset  when  the  variable
                     that has expanded is assigned a new value.
              .sh.name
                     Set to the name of the variable at the time that a disci-
                     pline function is invoked.
              .sh.subscript
                     Set to the name subscript of the  variable  at  the  time
                     that a discipline function is invoked.
              .sh.subshell
                     The current depth for subshells and command substitution.
              .sh.value
                     Set to the value of the variable at the time that the set
                     or append discipline function is invoked.
              .sh.version
                     Set to a value that identifies the version of this shell.
              KSH_VERSION
                     A name reference to .sh.version.
              LINENO The current line number within  the  script  or  function
                     being executed.
              OLDPWD The previous working directory set by the cd command.
              OPTARG The  value  of  the last option argument processed by the
                     getopts built-in command.
              OPTIND The index of the last option argument  processed  by  the
                     getopts built-in command.
              PPID   The process number of the parent of the shell.
              PWD    The present working directory set by the cd command.
              RANDOM Each  time this variable is referenced, a random integer,
                     uniformly distributed between 0 and 32767, is  generated.
                     The  sequence  of  random  numbers  can be initialized by
                     assigning a numeric value to RANDOM.
              REPLY  This variable is set by the select statement and  by  the
                     read built-in command when no arguments are supplied.
              SECONDS
                     Each time this variable is referenced, the number of sec-
                     onds since shell invocation is returned.  If  this  vari-
                     able  is  assigned  a value, then the value returned upon
                     reference will be the value that was  assigned  plus  the
                     number of seconds since the assignment.
              SHLVL  An  integer  variable  the  is  incremented each time the
                     shell is invoked and is exported.  If SHLVL is not in the
                     environment when the shell is invoked, it is set to 1.

       The following variables are used by the shell:
              CDPATH The search path for the cd command.
              COLUMNS
                     If  this variable is set, the value is used to define the
                     width of the edit window for the shell edit modes and for
                     printing select lists.
              EDITOR If  the  VISUAL  variable  is  not set, the value of this
                     variable will be checked for the  patterns  as  described
                     with  VISUAL  below  and the corresponding editing option
                     (see Special Command set below) will be turned on.
              ENV    If this variable is set, then parameter  expansion,  com-
                     mand  substitution,  and arithmetic substitution are per-
                     formed on the value  to  generate  the  pathname  of  the
                     script  that  will  be executed when the shell is invoked
                     interactively (see Invocation below).  This file is typi-
                     cally  used  for  alias  and  function  definitions.  The
                     default value is $HOME/.kshrc.  On systems that support a
                     system  wide   /etc/ksh.kshrc initialization file, if the
                     filename generated by the expansion of  ENV  begins  with
                     /./  or ././ the system wide initialization file will not
                     be executed.
              FCEDIT Obsolete name for the default editor name  for  the  hist
                     command.  FCEDIT is not used when HISTEDIT is set.
              FIGNORE
                     A  pattern that defines the set of filenames that will be
                     ignored when performing filename matching.
              FPATH  The search path for function definitions.   The  directo-
                     ries  in  this path are searched for a file with the same
                     name as the function or command when a function with  the
                     -u  attribute  is  referenced  and  when a command is not
                     found.  If an executable file with the name of that  com-
                     mand  is  found, then it is read and executed in the cur-
                     rent environment.  Unlike  PATH,  the  current  directory
                     must  be  represented  explicitly  by  .   rather than by
                     adjacent : characters or a beginning or ending :.
              HISTCMD
                     Number of the current command in the history file.
              HISTEDIT
                     Name for the default editor name for the hist command.
              HISTFILE
                     If this variable is set when the shell is  invoked,  then
                     the  value  is the pathname of the file that will be used
                     to  store  the  command  history  (see  Command  Re-entry
                     below).
              HISTSIZE
                     If  this  variable is set when the shell is invoked, then
                     the number of previously entered commands that are acces-
                     sible by this shell will be greater than or equal to this
                     number.  The default is 512.
              HOME   The default argument (home directory) for the cd command.
              IFS    Internal  field separators, normally space, tab, and new-
                     line that are used to separate  the  results  of  command
                     substitution  or  parameter  expansion  and  to  separate
                     fields with the built-in command read.  The first charac-
                     ter of the IFS variable is used to separate arguments for
                     the "$*" substitution (see Quoting below).   Each  single
                     occurrence of an IFS character in the string to be split,
                     that is not in the isspace character class, and any adja-
                     cent  characters in IFS that are in the isspace character
                     class, delimit a field.  One or more  characters  in  IFS
                     that  belong  to  the  isspace character class, delimit a
                     field.   In  addition,  if  the  same  isspace  character
                     appears  consecutively  inside  IFS,  this  character  is
                     treated as if it were not in the isspace class,  so  that
                     if  IFS consists of two tab characters, then two adjacent
                     tab characters delimit a null field.
              JOBMAX This variable defines the maximum  number  running  back-
                     ground  jobs  that can run at a time.  When this limit is
                     reached, the shell will wait for a job to complete before
                     staring a new job.
              LANG   This variable determines the locale category for any cat-
                     egory not specifically selected with a variable  starting
                     with LC_ or LANG.
              LC_ALL This  variable  overrides  the value of the LANG variable
                     and any other LC_ variable.
              LC_COLLATE
                     This variable determines the locale category for  charac-
                     ter collation information.
              LC_CTYPE
                     This  variable determines the locale category for charac-
                     ter handling  functions.   It  determines  the  character
                     classes  for  pattern  matching (see File Name Generation
                     below).
              LC_NUMERIC
                     This variable determines the locale category for the dec-
                     imal point character.
              LINES  If  this  variable is set, the value is used to determine
                     the column length  for  printing  select  lists.   Select
                     lists  will  print  vertically  until about two-thirds of
                     LINES lines are filled.
              MAIL   If this variable is set to the name of a  mail  file  and
                     the  MAILPATH variable is not set, then the shell informs
                     the user of arrival of mail in the specified file.
              MAILCHECK
                     This variable specifies how often (in seconds) the  shell
                     will check for changes in the modification time of any of
                     the files specified by the MAILPATH  or  MAIL  variables.
                     The  default  value  is  600  seconds.  When the time has
                     elapsed the shell will  check  before  issuing  the  next
                     prompt.
              MAILPATH
                     A  colon  (  :  )  separated list of file names.  If this
                     variable is set, then the shell informs the user  of  any
                     modifications  to  the specified files that have occurred
                     within the last MAILCHECK seconds.  Each file name can be
                     followed by a ?  and a message that will be printed.  The
                     message will undergo parameter expansion, command substi-
                     tution,  and arithmetic substitution with the variable $_
                     defined as the name of the file that  has  changed.   The
                     default message is you have mail in $_.
              PATH   The  search path for commands (see Execution below).  The
                     user may not change PATH if executing under rksh  (except
                     in .profile).
              PS1    The  value  of  this  variable  is expanded for parameter
                     expansion, command substitution, and arithmetic substitu-
                     tion to define the primary prompt string which by default
                     is ''$''.  The character !  in the primary prompt  string
                     is  replaced  by the command number (see Command Re-entry
                     below).  Two successive occurrences of !  will produce  a
                     single !  when the prompt string is printed.
              PS2    Secondary prompt string, by default ''> ''.
              PS3    Selection  prompt  string  used  within a select loop, by
                     default ''#? ''.
              PS4    The value of this  variable  is  expanded  for  parameter
                     evaluation,  command substitution, and arithmetic substi-
                     tution and precedes each line of an execution trace.   By
                     default,  PS4  is ''+ ''.  In addition when PS4 is unset,
                     the execution trace prompt is also ''+ ''.
              SHELL  The pathname of the shell is kept in the environment.  At
                     invocation,  if  the  basename  of  this variable is rsh,
                     rksh, or krsh, then the shell becomes restricted.  If  it
                     is  pfsh or pfksh, then the shell becomes a profile shell
                     (see pfexec(1)).
              TIMEFORMAT
                     The value of this parameter is used as  a  format  string
                     specifying  how the timing information for pipelines pre-
                     fixed with the time reserved word  should  be  displayed.
                     The  %  character  introduces  a  format sequence that is
                     expanded to a time value or other information.  The  for-
                     mat sequences and their meanings are as follows.
                     %%        A literal %.
                     %[p][l]R  The elapsed time in seconds.
                     %[p][l]U  The number of CPU seconds spent in user mode.
                     %[p][l]S  The number of CPU seconds spent in system mode.
                     %P        The CPU percentage, computed as (U + S) / R.

                     The brackets denote optional portions.  The optional p is
                     a  digit  specifying  the  precision, the number of frac-
                     tional digits after a decimal point.  A value of 0 causes
                     no decimal point or fraction to be output.  At most three
                     places after the decimal point can be  displayed;  values
                     of p greater than 3 are treated as 3.  If p is not speci-
                     fied, the value 3 is used.

                     The optional l specifies a longer format, including hours
                     if  greater  than  zero, minutes, and seconds of the form
                     HHhMMmSS.FFs.  The value of p determines whether  or  not
                     the fraction is included.

                     All  other  characters  are  output  without change and a
                     trailing newline is added.  If unset, the default  value,
                     $'\nreal\t%2lR\nuser\t%2lU\nsys%2lS',  is  used.   If the
                     value is null, no timing information is displayed.

              TMOUT  If set to a value greater than zero, TMOUT  will  be  the
                     default timeout value for the read built-in command.  The
                     select compound command terminates  after  TMOUT  seconds
                     when input is from a terminal.  Otherwise, the shell will
                     terminate if a line is not entered within the  prescribed
                     number  of  seconds while reading from a terminal.  (Note
                     that the shell can be compiled with a maximum  bound  for
                     this value which cannot be exceeded.)

              VISUAL If  the  value  of  this  variable  matches  the  pattern
                     *[Vv][Ii]*, then the vi option (see Special  Command  set
                     below)  is  turned  on.  If the value matches the pattern
                     *gmacs* , the gmacs option is turned on.   If  the  value
                     matches the pattern *macs*, then the emacs option will be
                     turned on.  The value of VISUAL overrides  the  value  of
                     EDITOR.

       The  shell gives default values to PATH, PS1, PS2, PS3, PS4, MAILCHECK,
       FCEDIT, TMOUT and IFS, while HOME, SHELL, ENV, and MAIL are not set  at
       all  by  the shell (although HOME is set by login(1)).  On some systems
       MAIL and SHELL are also set by login(1).

   Field Splitting.
       After parameter expansion and command substitution, the results of sub-
       stitutions  are scanned for the field separator characters (those found
       in IFS) and split into distinct fields where such characters are found.
       Explicit  null  fields  (""  or ??) are retained.  Implicit null fields
       (those resulting from parameters that have no values or command substi-
       tutions with no output) are removed.

       If the braceexpand (-B) option is set then each of the fields resulting
       from IFS are checked to see if they contain one or more  of  the  brace
       patterns  {*,*},  {l1..l2} , {n1..n2} , {n1..n2% fmt} , {n1..n2 ..n3} ,
       or {n1..n2 ..n3%fmt} , where * represents any character, l1,l2 are let-
       ters  and  n1,n2,n3 are signed numbers and fmt is a format specified as
       used by printf.  In each case, fields are  created  by  prepending  the
       characters  before  the  {  and appending the characters after the } to
       each of the strings generated by the characters between the  {  and  }.
       The  resulting  fields  are  checked to see if they have any brace pat-
       terns.

       In the first form, a field is created for each string between { and  ,,
       between  , and ,, and between , and }.  The string represented by * can
       contain embedded matching { and } without quoting.  Otherwise,  each  {
       and } with * must be quoted.

       In  the  seconds form, l1 and l2 must both be either upper case or both
       be lower case characters in the C locale.  In this case a field is cre-
       ated for each character from l1 thru l2.

       In  the remaining forms, a field is created for each number starting at
       n1 and continuing until it reaches n2 incrementing n1 by n3.  The cases
       where n3 is not specified behave as if n3 where 1 if n1<=n2 and -1 oth-
       erwise.  If forms which specify %fmt any format flags, widths and  pre-
       cisions  can  be  specified  and  fmt  can end in any of the specifiers
       cdiouxX.  For  example,  {a,z}{1..5..3%02d}{b..c}x  expands  to  the  8
       fields, a01bx, a01cx, a04bx, a04cx, z01bx, z01cx, z04bx and z4cx.

   File Name Generation.
       Following  splitting, each field is scanned for the characters *, ?, (,
       and [ unless the -f option has been set.  If one  of  these  characters
       appears, then the word is regarded as a pattern.  Each file name compo-
       nent that contains any pattern character is  replaced  with  a  lexico-
       graphically  sorted  set  of  names  that matches the pattern from that
       directory.  If no file name is found that  matches  the  pattern,  then
       that  component of the filename is left unchanged unless the pattern is
       prefixed with ~(N) in which case it is removed as described below.   If
       FIGNORE  is set, then each file name component that matches the pattern
       defined by the value of FIGNORE is ignored when generating the matching
       filenames.   The  names .  and ..  are also ignored.  If FIGNORE is not
       set, the character .  at the start of each file name component will  be
       ignored unless the first character of the pattern corresponding to this
       component is the character .  itself.  Note, that  for  other  uses  of
       pattern matching the / and .  are not treated specially.

              *      Matches any string, including the null string.  When used
                     for filename expansion, if the globstar option is on, two
                     adjacent  *'s  by itself will match all files and zero or
                     more directories and subdirectories.  If followed by a  /
                     then only directories and subdirectories will match.
              ?      Matches any single character.
              [...]  Matches  any  one  of the enclosed characters.  A pair of
                     characters separated by - matches any character lexically
                     between the pair, inclusive.  If the first character fol-
                     lowing the opening [ is  a  !   then  any  character  not
                     enclosed  is matched.  A - can be included in the charac-
                     ter set by putting it as the first or last character.
                     Within [ and ], character classes can be  specified  with
                     the  syntax [:class:] where class is one of the following
                     classes defined in the ANSI-C standard: (Note  that  word
                     is equivalent to alnum plus the character _).
              alnum  alpha  blank  cntrl  digit  graph lower print punct space
              upper word xdigit
              Within [ and ], an equivalence class can be specified  with  the
              syntax  [=c=] which matches all characters with the same primary
              collation weight (as defined by the current locale) as the char-
              acter c.
              Within [ and ], [.symbol.]  matches the collating symbol symbol.
       A pattern-list is a list of one or more patterns  separated  from  each
       other  with  a & or |.  A & signifies that all patterns must be matched
       whereas | requires that only one pattern be  matched.   Composite  pat-
       terns can be formed with one or more of the following sub-patterns:
              ?(pattern-list)
                     Optionally matches any one of the given patterns.
              *(pattern-list)
                     Matches zero or more occurrences of the given patterns.
              +(pattern-list)
                     Matches one or more occurrences of the given patterns.
              {n}(pattern-list)
                     Matches n occurrences of the given patterns.
              {m,n}(pattern-list)
                     Matches  from  m  to n occurrences of the given patterns.
                     If m is omitted, 0 will be used.   If  n  is  omitted  at
                     least m occurrences will be matched.
              @(pattern-list)
                     Matches exactly one of the given patterns.
              !(pattern-list)
                     Matches anything except one of the given patterns.
       By  default, each pattern, or sub-pattern will match the longest string
       possible consistent with generating the longest overall match.  If more
       than  one  match is possible, the one starting closest to the beginning
       of the string will be chosen.   However, for each of the above compound
       patterns  a  -  can be inserted in front of the ( to cause the shortest
       match to the specified pattern-list to be used.

       When pattern-list is contained within parentheses, the backslash  char-
       acter  \ is treated specially even when inside a character class.   All
       ANSI-C character escapes are recognized and match the specified charac-
       ter.  In addition the following escape sequences are recognized:
              \d     Matches any character in the digit class.
              \D     Matches any character not in the digit class.
              \s     Matches any character in the space class.
              \S     Matches any character not in the space class.
              \w     Matches any character in the word class.
              \W     Matches any character not in the word class.

       A  pattern  of the form %(pattern-pair(s)) is a sub-pattern that can be
       used to match nested character expressions.  Each pattern-pair is a two
       character sequence which cannot contain & or |.  The first pattern-pair
       specifies the starting and ending characters for the match.  Each  sub-
       sequent  pattern-pair represents the beginning and ending characters of
       a nested group that will be skipped over  when  counting  starting  and
       ending  character  matches.  The behavior is unspecified when the first
       character of a pattern-pair is alpha-numeric except for the following:
              D      Causes the ending character to terminate the  search  for
                     this pattern without finding a match.
              E      Causes  the  ending  character  to  be  interpreted as an
                     escape character.
              L      Causes the ending character to be interpreted as a  quote
                     character causing all characters to be ignored when look-
                     ing for a match.
              Q      Causes the ending character to be interpreted as a  quote
                     character  causing  all  characters other than any escape
                     character to be ignored when looking for a match.
       Thus, %({}Q"E\), matches characters starting at { until the matching  }
       is  found not counting any { or } that is inside a double quoted string
       or preceded by the escape character \.  Without  the  {}  this  pattern
       matches any C language string.

       Each  sub-pattern in a composite pattern is numbered, starting at 1, by
       the location of the ( within the pattern.  The sequence \n, where n  is
       a  single  digit  and \n comes after the n-th. sub-pattern, matches the
       same string as the sub-pattern itself.

       Finally a pattern can contain sub-patterns of the  form  ~(options:pat-
       tern-list),  where  either  options  or  :pattern-list  can be omitted.
       Unlike the other compound patterns, these sub-patterns are not  counted
       in the numbered sub-patterns.  If options is present, it can consist of
       one or more of the following:
              +      Enable the following options.  This is the default.
              -      Disable the following options.
              E      The  remainder  of  the  pattern  uses  extended  regular
                     expression syntax like the egrep(1) command.
              F      The  remainder  of  the  pattern uses fgrep(1) expression
                     syntax.
              G      The remainder of the pattern uses basic  regular  expres-
                     sion syntax like the grep(1) command.
              K      The  remainder  of the pattern uses shell pattern syntax.
                     This is the default.
              N      This is ignored.  However, when it is  the  first  letter
                     and  is  used  with  file name generation, and no matches
                     occur, the file pattern expands to the empty string.
              i      Treat the match as case insensitive.
              g      File the longest match (greedy).  This is the default.
              l      Left anchor the pattern.  This is the default for K style
                     patterns.
              r      Right  anchor  the  pattern.   This  is the default for K
                     style patterns.
       If both options and :pattern-list are specified, then the options apply
       only to  pattern-list.  Otherwise, these options remain in effect until
       they are disabled by a subsequent ~(...) or at the end of the  sub-pat-
       tern containing ~(...).

   Quoting.
       Each of the metacharacters listed earlier (see Definitions above) has a
       special meaning to the shell and causes termination of  a  word  unless
       quoted.   A character may be quoted (i.e., made to stand for itself) by
       preceding it with a \.  The pair \new-line is removed.  All  characters
       enclosed between a pair of single quote marks (??) that is not preceded
       by a $ are quoted.  A single quote  cannot  appear  within  the  single
       quotes.   A single quoted string preceded by an unquoted $ is processed
       as an ANSI-C string except for the following:
       \0     Causes the remainder of the string to be ignored.
       \E     Equivalent to the escape character (ascii 033),
       \e     Equivalent to the escape character (ascii 033),
       \cx    Expands to the character control-x.
       \C[.name.]
              Expands to the collating element name.

       Inside double quote marks  (""),  parameter  and  command  substitution
       occur  and  \  quotes the characters \, `, ", and $.  A $ in front of a
       double quoted string will be ignored in the "C" or "POSIX" locale,  and
       may  cause the string to be replaced by a locale specific string other-
       wise.  The meaning of $* and $@ is identical when not  quoted  or  when
       used  as  a variable assignment value or as a file name.  However, when
       used as a command argument, "$*" is equivalent to "$1d$2d...", where  d
       is  the first character of the IFS variable, whereas "$@" is equivalent
       to "$1" "$2" ....  Inside grave quote marks (``), \ quotes the  charac-
       ters \, `, and $.  If the grave quotes occur within double quotes, then
       \ also quotes the character ".

       The special meaning of reserved words or  aliases  can  be  removed  by
       quoting  any  character of the reserved word.  The recognition of func-
       tion names or built-in command names listed below cannot be altered  by
       quoting them.

   Arithmetic Evaluation.
       The  shell  performs arithmetic evaluation for arithmetic substitution,
       to evaluate an arithmetic command, to evaluate an  indexed  array  sub-
       script,  and  to  evaluate arguments to the built-in commands shift and
       let.  Evaluations are performed using double precision  floating  point
       arithmetic  or  long  double  precision floating point for systems that
       provide this data type.  Floating point  constants  follow  the  ANSI-C
       programming  language  floating  point  conventions.  Integer constants
       follow the ANSI-C programming  language  integer  constant  conventions
       although  only single byte character constants are recognized and char-
       acter casts are not recognized.  In addition constants can  be  of  the
       form [base#]n where base is a decimal number between two and sixty-four
       representing the arithmetic base and n is a number in that  base.   The
       digits  above  9  are  represented by the lower case letters, the upper
       case letters, @, and _ respectively.  For bases less than or  equal  to
       36, upper and lower case characters can be used interchangeably.

       An arithmetic expression uses the same syntax, precedence, and associa-
       tivity of expression as the C language.  All the C  language  operators
       that  apply to floating point quantities can be used.  In addition, the
       operator ** can be used for exponentiation.  It has  higher  precedence
       than  multiplication  and  is  left associative.  In addition, when the
       value of an arithmetic variable or sub-expression can be represented as
       a  long  integer,  all  C language integer arithmetic operations can be
       performed.  Variables can be referenced by name  within  an  arithmetic
       expression  without using the parameter expansion syntax.  When a vari-
       able is referenced, its value is evaluated as an arithmetic expression.

       Any  of  the  following  math  library functions that are in the C math
       library can be used within an arithmetic expression:

       abs acos acosh asin asinh atan atan2 atanh cbrt copysign cos  cosh  erf
       erfc  exp  exp2  expm1 fabs fdim finite floor fma fmax fmod hypot ilogb
       int isinf isnan j0 j1 jn lgamma log log2 logb nearbyint nextafter next-
       toward  pow remainder rint round sin sinh sqrt tan tanh tgamma trunc y0
       y1 yn

       An internal representation of a variable as a double precision floating
       point can be specified with the -E [n], -F [n], or -X [n] option of the
       typeset special built-in command.  The -E option causes  the  expansion
       of  the  value  to  be represented using scientific notation when it is
       expanded.  The optional option argument n defines the number of signif-
       icant figures.  The -F option causes the expansion to be represented as
       a floating decimal number when it is expanded.  The -X option cause the
       expansion  to  be  represented using the %a format defined by ISO C-99.
       The optional option argument n defines the number of places  after  the
       decimal (or radix) point in this case.

       An  internal integer representation of a variable can be specified with
       the -i [n]  option  of  the  typeset  special  built-in  command.   The
       optional option argument n specifies an arithmetic base to be used when
       expanding the variable.  If you do not specify an arithmetic base, base
       10 will be used.

       Arithmetic evaluation is performed on the value of each assignment to a
       variable with the -E, -F, -X, or -i attribute.   Assigning  a  floating
       point  number  to  a variable whose type is an integer causes the frac-
       tional part to be truncated.

   Prompting.
       When used interactively, the shell prompts with the value of PS1  after
       expanding  it for parameter expansion, command substitution, and arith-
       metic substitution, before reading a command.  In addition, each single
       !   in the prompt is replaced by the command number.  A !!  is required
       to place !  in the prompt.  If at any time a new-line is typed and fur-
       ther  input  is needed to complete a command, then the secondary prompt
       (i.e., the value of PS2) is issued.

   Conditional Expressions.
       A conditional expression is used with the [[ compound command  to  test
       attributes  of  files and to compare strings.  Field splitting and file
       name generation are not performed on the words between [[ and ]].  Each
       expression  can  be constructed from one or more of the following unary
       or binary expressions:
       string True, if string is not null.
       -a file
              Same as -e below.  This is obsolete.
       -b file
              True, if file exists and is a block special file.
       -c file
              True, if file exists and is a character special file.
       -d file
              True, if file exists and is a directory.
       -e file
              True, if file exists.
       -f file
              True, if file exists and is an ordinary file.
       -g file
              True, if file exists and it has its setgid bit set.
       -k file
              True, if file exists and it has its sticky bit set.
       -n string
              True, if length of string is non-zero.
       -o ?option
              True, if option named option is a valid option name.
       -o option
              True, if option named option is on.
       -p file
              True, if file exists and is a fifo special file or a pipe.
       -r file
              True, if file exists and is readable by current process.
       -s file
              True, if file exists and has size greater than zero.
       -t fildes
              True, if file descriptor number fildes is  open  and  associated
              with a terminal device.
       -u file
              True, if file exists and it has its setuid bit set.
       -w file
              True, if file exists and is writable by current process.
       -x file
              True,  if  file exists and is executable by current process.  If
              file exists and is a directory, then true if the current process
              has permission to search in the directory.
       -z string
              True, if length of string is zero.
       -L file
              True, if file exists and is a symbolic link.
       -h file
              True, if file exists and is a symbolic link.
       -N file
              True,  if  file exists and the modification time is greater than
              the last access time.
       -O file
              True, if file exists and is owned by the effective  user  id  of
              this process.
       -G file
              True,  if  file exists and its group matches the effective group
              id of this process.
       -S file
              True, if file exists and is a socket.
       file1 -nt file2
              True, if file1 exists and file2 does not, or file1 is newer than
              file2.
       file1 -ot file2
              True, if file2 exists and file1 does not, or file1 is older than
              file2.
       file1 -ef file2
              True, if file1 and file2 exist and refer to the same file.
       string == pattern
              True, if string matches pattern.  Any part  of  pattern  can  be
              quoted to cause it to be matched as a string.  With a successful
              match to a pattern, the .sh.match array  variable  will  contain
              the match and sub-pattern matches.
       string = pattern
              Same as == above, but is obsolete.
       string != pattern
              True, if string does not match pattern.  When the string matches
              the pattern the .sh.match array variable will contain the  match
              and sub-pattern matches.
       string =~ ere
              True  if  string  matches  the  pattern  ~(E)ere where ere is an
              extended regular expression.
       string1 < string2
              True, if string1 comes before string2 based on  ASCII  value  of
              their characters.
       string1 > string2
              True,  if  string1  comes  after string2 based on ASCII value of
              their characters.
       The following obsolete arithmetic comparisons are also permitted:
       exp1 -eq exp2
              True, if exp1 is equal to exp2.
       exp1 -ne exp2
              True, if exp1 is not equal to exp2.
       exp1 -lt exp2
              True, if exp1 is less than exp2.
       exp1 -gt exp2
              True, if exp1 is greater than exp2.
       exp1 -le exp2
              True, if exp1 is less than or equal to exp2.
       exp1 -ge exp2
              True, if exp1 is greater than or equal to exp2.

       In each of the above expressions, if file is  of  the  form  /dev/fd/n,
       where  n is an integer, then the test is applied to the open file whose
       descriptor number is n.

       A compound expression can be constructed from these primitives by using
       any of the following, listed in decreasing order of precedence.
       (expression)
              True, if expression is true.  Used to group expressions.
       ! expression
              True if expression is false.
       expression1 && expression2
              True, if expression1 and expression2 are both true.
       expression1 || expression2
              True, if either expression1 or expression2 is true.

   Input/Output.
       Before  a  command  is executed, its input and output may be redirected
       using a special notation interpreted by the shell.  The  following  may
       appear  anywhere in a simple-command or may precede or follow a command
       and are not passed on to the invoked  command.   Command  substitution,
       parameter  expansion,  and arithmetic substitution occur before word or
       digit is used except as noted below.  File name generation occurs  only
       if  the  shell  is  interactive  and the pattern matches a single file.
       Field splitting is not performed.

       In each  of  the  following  redirections,  if  file  is  of  the  form
       /dev/sctp/host/port,  /dev/tcp/host/port,  or /dev/udp/host/port, where
       host is a hostname or host address, and port is a service given by name
       or an integer port number, then the redirection attempts to make a tcp,
       sctp or udp connection to the corresponding socket.

       No intervening space is allowed between the characters  of  redirection
       operators.

       <word         Use file word as standard input (file descriptor 0).

       >word         Use file word as standard output (file descriptor 1).  If
                     the file does not exist then it is created.  If the  file
                     exists,  and  the  noclobber option is on, this causes an
                     error; otherwise, it is truncated to zero length.

       >|word        Sames as  >,  except  that  it  overrides  the  noclobber
                     option.

       >;word        Write  output  to  a temporary file.  If the command com-
                     pletes successfully rename it to word, otherwise,  delete
                     the  temporary  file.   >;word  cannot  be  used with the
                     exec(2).  built-in.

       >>word        Use file word as standard output.  If  the  file  exists,
                     then  output  is  appended to it (by first seeking to the
                     end-of-file); otherwise, the file is created.

       <>word        Open file word for reading and writing as  standard  out-
                     put.

       <>;word       The  same  as <>word except that if the command completes
                     successfully, word is truncated to the offset at  command
                     completion.   <>;word  cannot  be  used with the exec(2).
                     built-in.

       <<[-]word     The shell input is read up to a line that is the same  as
                     word after any quoting has been removed, or to an end-of-
                     file.  No parameter substitution,  command  substitution,
                     arithmetic  substitution  or file name generation is per-
                     formed on word.  The resulting document, called  a  here-
                     document,  becomes  the standard input.  If any character
                     of word is quoted, then no interpretation is placed  upon
                     the  characters  of  the  document;  otherwise, parameter
                     expansion, command substitution, and arithmetic substitu-
                     tion  occur,  \new-line is ignored, and \ must be used to
                     quote the characters \, $, `.  If - is  appended  to  <<,
                     then all leading tabs are stripped from word and from the
                     document.  If # is appended to <<,  then  leading  spaces
                     and tabs will be stripped off the first line of the docu-
                     ment and up to an equivalent indentation will be stripped
                     from  the  remaining  lines and from word.  A tab stop is
                     assumed to occur at every 8 columns for the  purposes  of
                     determining the indentation.

       <<<word       A  short  form of here document in which word becomes the
                     contents of the here-document after any parameter  expan-
                     sion,  command  substitution, and arithmetic substitution
                     occur.

       <&digit       The standard input is  duplicated  from  file  descriptor
                     digit  (see  dup(2)).   Similarly for the standard output
                     using >&digit.

       <&digit-      The file descriptor given by digit is moved  to  standard
                     input.  Similarly for the standard output using >&digit-.

       <&-           The standard input is closed.  Similarly for the standard
                     output using >&-.

       <&p           The input from the co-process is moved to standard input.

       >&p           The output to the co-process is moved to standard output.

       <#((expr))    Evaluate  arithmetic  expression  expr  and position file
                     descriptor 0 to the resulting value bytes from the  start
                     of  the  file.  The variables CUR and EOF evaluate to the
                     current offset and end-of-file offset  respectively  when
                     evaluating expr.

       >#((offset))  The same as <# except applies to file descriptor 1.

       <#pattern     Seeks  forward to the beginning of the next line contain-
                     ing pattern.

       <##pattern    The same as <# except that the portion of the  file  that
                     is skipped is copied to standard output.

       If  one of the above is preceded by a digit, with no intervening space,
       then the file descriptor number referred to is that  specified  by  the
       digit (instead of the default 0 or 1).  If one of the above, other than
       >&- and the  >#  and  <#  forms,  is  preceded  by  {varname}  with  no
       intervening  space, then a file descriptor number > 10 will be selected
       by the shell and stored in the variable varname.  If >&- or the any  of
       the  >#  and  <#  forms  is  preceded by {varname} the value of varname
       defines the file descriptor to close or position.  For example:

              ... 2>&1

       means file descriptor 2 is to be opened for writing as a  duplicate  of
       file descriptor 1 and

              exec {n}<file

       means  open  file  named file for reading and store the file descriptor
       number in variable n.

       The order in which redirections  are  specified  is  significant.   The
       shell  evaluates  each  redirection  in  terms of the (file descriptor,
       file) association at the time of evaluation.  For example:

              ... 1>fname 2>&1

       first associates file descriptor 1 with file fname.  It then associates
       file descriptor 2 with the file associated with file descriptor 1 (i.e.
       fname).  If the order of redirections were reversed, file descriptor  2
       would  be  associated with the terminal (assuming file descriptor 1 had
       been) and then file descriptor 1 would be associated with file fname.

       If a command is followed by & and job control is not active,  then  the
       default  standard  input  for  the command is the empty file /dev/null.
       Otherwise, the environment for the execution of a command contains  the
       file  descriptors  of  the  invoking  shell as modified by input/output
       specifications.

   Environment.
       The environment (see environ(7)) is a list of name-value pairs that  is
       passed  to  an  executed  program  in the same way as a normal argument
       list.  The names must be  identifiers  and  the  values  are  character
       strings.  The shell interacts with the environment in several ways.  On
       invocation, the shell scans the environment and creates a variable  for
       each  name  found, giving it the corresponding value and attributes and
       marking it export.  Executed commands inherit the environment.  If  the
       user  modifies the values of these variables or creates new ones, using
       the export or typeset -x commands, they become part of the environment.
       The  environment  seen  by any executed command is thus composed of any
       name-value pairs originally inherited by the shell, whose values may be
       modified  by  the current shell, plus any additions which must be noted
       in export or typeset -x commands.

       The environment for any simple-command or function may be augmented  by
       prefixing it with one or more variable assignments.  A variable assign-
       ment argument is a word of the form identifier=value.  Thus:

              TERM=450 cmd args                  and
              (export TERM; TERM=450; cmd args)

       are equivalent (as far as the  above  execution  of  cmd  is  concerned
       except for special built-in commands listed below - those that are pre-
       ceded with a dagger).

       If the obsolete -k option is set, all variable assignment arguments are
       placed  in  the environment, even if they occur after the command name.
       The following first prints a=b c and then c:

              echo a=b c
              set -k
              echo a=b c
       This feature is intended for use with scripts written  for  early  ver-
       sions  of the shell and its use in new scripts is strongly discouraged.
       It is likely to disappear someday.

   Functions.
       For historical reasons, there are two ways  to  define  functions,  the
       name()  syntax  and the function name syntax, described in the Commands
       section above.  Shell functions are  read  in  and  stored  internally.
       Alias names are resolved when the function is read.  Functions are exe-
       cuted like commands with the arguments passed as positional parameters.
       (See Execution below.)

       Functions  defined  by the function name syntax and called by name exe-
       cute in the same process as the caller and share all files and  present
       working  directory  with  the  caller.   Traps caught by the caller are
       reset to their default action inside the function.   A  trap  condition
       that  is  not  caught or ignored by the function causes the function to
       terminate and the condition to be passed on to the caller.  A  trap  on
       EXIT set inside a function is executed in the environment of the caller
       after the function completes.  Ordinarily, variables are shared between
       the  calling  program  and  the function.  However, the typeset special
       built-in command used within a function defines local  variables  whose
       scope  includes  the current function.  They can be passed to functions
       that they call in the variable assignment list that precedes  the  call
       or  as  arguments  passed  as name references.  Errors within functions
       return control to the caller.

       Functions defined with the name() syntax and functions defined with the
       function  name syntax that are invoked with the .  special built-in are
       executed in the caller's environment and share all variables and  traps
       with  the  caller.   Errors  within these function executions cause the
       script that contains them to abort.

       The special built-in command return is used  to  return  from  function
       calls.

       Function  names  can  be listed with the -f or +f option of the typeset
       special built-in command.  The text of functions, when available,  will
       also  be listed with -f.  Functions can be undefined with the -f option
       of the unset special built-in command.

       Ordinarily, functions are unset when the shell executes a shell script.
       Functions  that  need  to be defined across separate invocations of the
       shell should be placed in a directory and  the  FPATH  variable  should
       contain  the name of this directory.  They may also be specified in the
       ENV file.

   Discipline Functions.
       Each variable can have zero or  more  discipline  functions  associated
       with  it.   The  shell  initially understands the discipline names get,
       set, append, and unset but can be added when defining  new  types.   On
       most  systems  others  can  be  added at run time via the C programming
       interface extension provided by the builtin built-in utility.   If  the
       get  discipline  is  defined for a variable, it is invoked whenever the
       given variable is referenced.  If the variable .sh.value is assigned  a
       value  inside  the  discipline  function,  the referenced variable will
       evaluate to this value instead.  If the set discipline is defined for a
       variable,  it  is  invoked  whenever  the  given variable is assigned a
       value.  If the append discipline is  defined  for  a  variable,  it  is
       invoked  whenever a value is appended to the given variable.  The vari-
       able .sh.value is given the value of the variable before  invoking  the
       discipline,  and  the  variable will be assigned the value of .sh.value
       after the discipline completes.  If .sh.value is unset inside the  dis-
       cipline,  then  that  value  is  unchanged.  If the unset discipline is
       defined for a variable, it is invoked whenever the  given  variable  is
       unset.   The  variable  will not be unset unless it is unset explicitly
       from within this discipline function.

       The variable .sh.name contains the name of the variable for  which  the
       discipline  function  is  called, .sh.subscript is the subscript of the
       variable, and .sh.value will contain the value  being  assigned  inside
       the  set  discipline  function.   The  variable _ is a reference to the
       variable including the subscript  if  any.   For  the  set  discipline,
       changing  .sh.value will change the value that gets assigned.  Finally,
       the expansion ${var.name}, when name is the name of a  discipline,  and
       there is no variable of this name, is equivalent to the command substi-
       tution ${ var.name;}.

   Type Variables.
       Typed variables provide a way to create data structure and objects.   A
       type  can  be  defined either by a shared library, by the enum built-in
       command described below, or by using the new -T option of  the  typeset
       built-in command.  With the -T option of typeset, the type name, speci-
       fied as an option argument to -T,  is  set  with  a  compound  variable
       assignment  that  defines  the  type.   Function definitions can appear
       inside the compound variable assignment  and  these  become  discipline
       functions  for  this  type  and  can  be  invoked  or redefined by each
       instance of the type.  The function name create is  treated  specially.
       It  is invoked for each instance of the type that is created but is not
       inherited and cannot be redefined for each instance.

       When a type is defined a special  built-in  command  of  that  name  is
       added.   These  built-ins  are declaration commands and follow the same
       expansion rules as all the special built-in commands defined below that
       are  preceded  by  ++.   These commands can subsequently be used inside
       further type definitions.  The man page for these commands can be  gen-
       erated  by  using  the  --man  option  or  any  of the other -- options
       described with getopts.  The -r, -a, -A, -h, and -S options of  typeset
       are permitted with each of these new built-ins.

       An  instance of a type is created by invoking the type name followed by
       one or more instance names.  Each instance of the type  is  initialized
       with  a  copy  of  the  sub-variables except for sub-variables that are
       defined with the -S option.  Variables defined with the -S  are  shared
       by  all  instances  of the type.  Each instance can change the value of
       any sub-variable and can also define new discipline  functions  of  the
       same names as those defined by the type definition as well as any stan-
       dard discipline names.  No additional sub-variables can be defined  for
       any instance.

       When defining a type, if the value of a sub-variable is not set and the
       -r attribute is specified, it causes the sub-variable to be a  required
       sub-variable.   Whenever an instance of a type is created, all required
       sub-variables must be specified.  These sub-variables  become  readonly
       in each instance.

       When  unset  is  invoked  on  a  sub-variable within a type, and the -r
       attribute has not been specified for this field, the value is reset  to
       the  default value associative with the type.  Invoking unset on a type
       instance not contained within another type  deletes  all  sub-variables
       and the variable itself.

       A type definition can be derived from another type definition by defin-
       ing the first sub-variable name as _ and defining its type as the  base
       type.   Any  remaining  definitions will be additions and modifications
       that apply to the new type.  If the new type name is the same  is  that
       of  the base type, the type will be replaced and the original type will
       no longer be accessible.

   Jobs.
       If the monitor option of the set command is turned on,  an  interactive
       shell associates a job with each pipeline.  It keeps a table of current
       jobs, printed by the jobs command, and assigns them small integer  num-
       bers.   When a job is started asynchronously with &, the shell prints a
       line which looks like:

            [1] 1234

       indicating that the job which was started asynchronously was job number
       1 and had one (top-level) process, whose process id was 1234.

       This  paragraph  and the next require features that are not in all ver-
       sions of UNIX and may not apply.  If you are running a job and wish  to
       do something else you may hit the key ^Z (control-Z) which sends a STOP
       signal to the current job.  The shell will then normally indicate  that
       the  job  has  been  'Stopped', and print another prompt.  You can then
       manipulate the state of this job, putting it in the background with the
       bg  command,  or  run some other commands and then eventually bring the
       job back into the foreground with the  foreground  command  fg.   A  ^Z
       takes  effect immediately and is like an interrupt in that pending out-
       put and unread input are discarded when it is typed.

       A job being run in the background will stop if it tries  to  read  from
       the  terminal.  Background jobs are normally allowed to produce output,
       but this can be disabled by giving the command stty tostop.  If you set
       this  tty  option, then background jobs will stop when they try to pro-
       duce output like they do when they try to read input.

       There are several ways to refer to jobs in the shell.   A  job  can  be
       referred  to  by  the process id of any process of the job or by one of
       the following:
       %number
              The job with the given number.
       %string
              Any job whose command line begins with string.
       %?string
              Any job whose command line contains string.
       %%     Current job.
       %+     Equivalent to %%.
       %-     Previous job.

       The shell learns immediately whenever a process changes state.  It nor-
       mally  informs  you  whenever  a job becomes blocked so that no further
       progress is possible, but only just before it prints a prompt.  This is
       done  so  that  it  does  not  otherwise disturb your work.  The notify
       option of the set command causes the shell to print  these  job  change
       messages as soon as they occur.

       When the monitor option is on, each background job that completes trig-
       gers any trap set for CHLD.

       When you try to leave the shell while jobs are running or stopped,  you
       will  be warned that 'You have stopped(running) jobs.'  You may use the
       jobs command to see what they are.  If  you  immediately  try  to  exit
       again,  the shell will not warn you a second time, and the stopped jobs
       will be terminated.  When a login shell receives a HUP signal, it sends
       a  HUP  signal  to  each job that has not been disowned with the disown
       built-in command described below.

   Signals.
       The INT and QUIT signals for an invoked command are ignored if the com-
       mand is followed by & and the monitor option is not active.  Otherwise,
       signals have the values inherited by the shell from its parent (but see
       also the trap built-in command below).

   Execution.
       Each  time  a command is read, the above substitutions are carried out.
       If the command name matches one of the Special Built-in Commands listed
       below, it is executed within the current shell process.  Next, the com-
       mand name is checked to see if it matches a user defined function.   If
       it  does,  the  positional  parameters  are saved and then reset to the
       arguments of the function call.  A function is  also  executed  in  the
       current shell process.  When the function completes or issues a return,
       the positional parameter list is restored.  For functions defined  with
       the  function  name syntax, any trap set on EXIT within the function is
       executed.  The exit value of a function is the value of the  last  com-
       mand  executed.  If a command name is not a special built-in command or
       a user defined function, but it is one of the built-in commands  listed
       below, it is executed in the current shell process.

       The  shell variable PATH defines the search path for the directory con-
       taining the command.  Alternative directory names are  separated  by  a
       colon (:).  The default path is equal to getconf PATH output.  The cur-
       rent directory can be specified by two or more adjacent colons, or by a
       colon  at  the  beginning or end of the path list.  If the command name
       contains a /, then the search path is not used.  Otherwise, each direc-
       tory  in  the path is searched for an executable file of the given name
       that is not a directory.  If found, and if the  shell  determines  that
       there is a built-in version of a command corresponding to a given path-
       name, this built-in is invoked in the current process.  If  found,  and
       this  directory  is  also contained in the value of the FPATH variable,
       then this file is loaded into the current shell environment  as  if  it
       were  the argument to the . command except that only preset aliases are
       expanded, and a function of the given name  is  executed  as  described
       above.   If not found, and the file .paths is found, and this file con-
       tains a line of the form FPATH=path where path names an existing direc-
       tory,  and  this directory contains a file of the given name, then this
       file is loaded into the current shell environment as  if  it  were  the
       argument  to the . special built-in command and a function of the given
       name is executed.  Otherwise, if found, a process  is  created  and  an
       attempt is made to execute the command via exec(2).

       When  an  executable  is  found,  the directory where it is found in is
       searched for a file named .paths.  If this file is found  and  it  con-
       tains  a line of the form BUILTIN_LIB=value , then the library named by
       value will be searched for as if it were an option argument to  builtin
       -f,  and  if  it contains a built-in of the specified name this will be
       executed instead of a command by this name.  Otherwise, if this file is
       found  and  it  contains  a line of the form name=value in the first or
       second line, then the environment variable name is modified by prepend-
       ing  the  directory specified by value to the directory list.  If value
       is not an absolute directory, then it specifies a directory relative to
       the  directory that the executable was found.  If the environment vari-
       able name does not already exist it will be added  to  the  environment
       list for the specified command.

       If  the  file  has  execute  permission but is not an a.out file, it is
       assumed to be a file containing shell commands.  A  separate  shell  is
       spawned  to  read  it.   All non-exported variables are removed in this
       case.  If the shell command file doesn't have read  permission,  or  if
       the  setuid and/or setgid bits are set on the file, then the shell exe-
       cutes an agent whose job it is to set up the  permissions  and  execute
       the  shell  with the shell command file passed down as an open file.  A
       parenthesized command is executed in a sub-shell without removing  non-
       exported variables.

   Command Re-entry.
       The  text  of  the  last HISTSIZE (default 512) commands entered from a
       terminal device is saved in a history file.  The file $HOME/.sh_history
       is  used if the HISTFILE variable is not set or if the file it names is
       not writable.  A shell can  access  the  commands  of  all  interactive
       shells which use the same named HISTFILE.  The built-in command hist is
       used to list or edit a portion of this file.  The portion of  the  file
       to be edited or listed can be selected by number or by giving the first
       character or characters of the command.  A single command or  range  of
       commands  can be specified.  If you do not specify an editor program as
       an argument to hist then the value of the variable  HISTEDIT  is  used.
       If  HISTEDIT is unset, the obsolete variable FCEDIT is used.  If FCEDIT
       is not defined, then /bin/ed is used.  The edited command(s) is printed
       and  re-executed  upon leaving the editor unless you quit without writ-
       ing.  The -s option (and in obsolete versions, the editor  name  -)  is
       used  to skip the editing phase and to re-execute the command.  In this
       case a substitution parameter of the form old=new can be used to modify
       the  command  before  execution.  For example, with the preset alias r,
       which is aliased to ?hist -s?, typing 'r bad=good  c'  will  re-execute
       the  most  recent command which starts with the letter c, replacing the
       first occurrence of the string bad with the string good.

   In-line Editing Options.
       Normally, each command line entered from a terminal  device  is  simply
       typed  followed by a new-line ('RETURN' or 'LINE FEED').  If either the
       emacs, gmacs, or vi option is active, the user  can  edit  the  command
       line.   To  be  in  either  of  these  edit modes set the corresponding
       option.  An editing option is  automatically  selected  each  time  the
       VISUAL or EDITOR variable is assigned a value ending in either of these
       option names.

       The editing features require that the user's terminal  accept  'RETURN'
       as  carriage return without line feed and that a space (' ') must over-
       write the current character on the screen.

       Unless the multiline option is on, the editing modes implement  a  con-
       cept  where  the  user is looking through a window at the current line.
       The window width is the value of COLUMNS if it  is  defined,  otherwise
       80.   If  the window width is too small to display the prompt and leave
       at least 8 columns to enter input, the prompt  is  truncated  from  the
       left.  If the line is longer than the window width minus two, a mark is
       displayed at the end of the window to notify the user.  As  the  cursor
       moves  and  reaches  the  window boundaries the window will be centered
       about the cursor.  The mark is a > (<, *) if the line  extends  on  the
       right (left, both) side(s) of the window.

       The  search  commands  in  each edit mode provide access to the history
       file.  Only strings are matched, not patterns, although a leading ^  in
       the  string  restricts the match to begin at the first character in the
       line.

       Each of the edit modes has an operation to list the files  or  commands
       that match a partially entered word.  When applied to the first word on
       the line, or the first word after a ;, |, &, or (, and  the  word  does
       not  begin  with  ~ or contain a /, the list of aliases, functions, and
       executable commands defined by the PATH variable that could  match  the
       partial word is displayed.  Otherwise, the list of files that match the
       given word is displayed.  If the partially entered word does  not  con-
       tain  any  file expansion characters, a * is appended before generating
       these lists.  After displaying the generated list, the  input  line  is
       redrawn.   These  operations  are  called command name listing and file
       name listing, respectively.  There are additional operations,  referred
       to  as  command name completion and file name completion, which compute
       the list of matching commands or files, but  instead  of  printing  the
       list,  replace  the current word with a complete or partial match.  For
       file name completion, if the match is unique, a / is  appended  if  the
       file is a directory and a space is appended if the file is not a direc-
       tory.  Otherwise, the longest common prefix for all the matching  files
       replaces  the  word.   For command name completion, only the portion of
       the file names after the last / are used to find  the  longest  command
       prefix.   If  only  a single name matches this prefix, then the word is
       replaced with the command name followed by a space.  When using  a  tab
       for  completion  that  does  not yield a unique match, a subsequent tab
       will provide a numbered list  of  matching  alternatives.   A  specific
       selection  can  be  made by entering the selection number followed by a
       tab.

   Key Bindings.
       The KEYBD trap can be used to intercept keys  as  they  are  typed  and
       change  the  characters that are actually seen by the shell.  This trap
       is executed after each character (or sequence of  characters  when  the
       first  character is ESC) is entered while reading from a terminal.  The
       variable .sh.edchar contains the character or character sequence  which
       generated  the  trap.   Changing  the  value  of .sh.edchar in the trap
       action causes the shell to behave as if the new value were entered from
       the keyboard rather than the original value.

       The  variable .sh.edcol is set to the input column number of the cursor
       at the time of the input.  The variable .sh.edmode is set to  ESC  when
       in  vi  insert  mode  (see below) and is null otherwise.  By prepending
       ${.sh.editmode} to a value assigned to .sh.edchar  it  will  cause  the
       shell to change to control mode if it is not already in this mode.

       This trap is not invoked for characters entered as arguments to editing
       directives, or while reading input for a character search.

   Emacs Editing Mode.
       This mode is entered by enabling either the emacs or gmacs option.  The
       only  difference between these two modes is the way they handle ^T.  To
       edit, the user moves the cursor to the  point  needing  correction  and
       then inserts or deletes characters or words as needed.  All the editing
       commands are control characters or escape sequences.  The notation  for
       control  characters  is caret (^) followed by the character.  For exam-
       ple, ^F is the notation for control F.  This is entered  by  depressing
       'f'  while  holding  down the 'CTRL' (control) key.  The 'SHIFT' key is
       not depressed.  (The notation ^?  indicates the DEL (delete) key.)

       The notation for escape sequences is M- followed by a  character.   For
       example,  M-f  (pronounced  Meta f) is entered by depressing ESC (ascii
       033) followed by 'f'.  (M-F would be the notation for ESC  followed  by
       'SHIFT' (capital) 'F'.)

       All  edit  commands operate from any place on the line (not just at the
       beginning).  Neither the 'RETURN' nor the 'LINE FEED'  key  is  entered
       after edit commands except when noted.

       ^F        Move cursor forward (right) one character.
       M-[C      Move cursor forward (right) one character.
       M-f       Move  cursor forward one word.  (The emacs editor's idea of a
                 word is a string of characters consisting  of  only  letters,
                 digits and underscores.)
       ^B        Move cursor backward (left) one character.
       M-[D      Move cursor backward (left) one character.
       M-b       Move cursor backward one word.
       ^A        Move cursor to start of line.
       M-[H      Move cursor to start of line.
       ^E        Move cursor to end of line.
       M-[Y      Move cursor to end of line.
       ^]char    Move cursor forward to character char on current line.
       M-^]char  Move cursor backward to character char on current line.
       ^X^X      Interchange the cursor and mark.
       erase     (User  defined erase character as defined by the stty(1) com-
                 mand, usually ^H or #.)  Delete previous character.
       lnext     (User defined  literal  next  character  as  defined  by  the
                 stty(1)  command,  or  ^V  if not defined.)  Removes the next
                 character's editing features (if any).
       ^D        Delete current character.
       M-d       Delete current word.
       M-^H      (Meta-backspace) Delete previous word.
       M-h       Delete previous word.
       M-^?      (Meta-DEL) Delete previous word (if your interrupt  character
                 is ^?  (DEL, the default) then this command will not work).
       ^T        Transpose  current  character  with  previous  character  and
                 advance the cursor in emacs  mode.   Transpose  two  previous
                 characters in gmacs mode.
       ^C        Capitalize current character.
       M-c       Capitalize current word.
       M-l       Change the current word to lower case.
       ^K        Delete  from  the cursor to the end of the line.  If preceded
                 by a numerical parameter whose value is less than the current
                 cursor  position,  then  delete from given position up to the
                 cursor.  If preceded by a numerical parameter whose value  is
                 greater  than  the  current cursor position, then delete from
                 cursor up to given cursor position.
       ^W        Kill from the cursor to the mark.
       M-p       Push the region from the cursor to the mark on the stack.
       kill      (User defined kill character as defined by the stty  command,
                 usually ^G or @.)  Kill the entire current line.  If two kill
                 characters are entered in  succession,  all  kill  characters
                 from  then on cause a line feed (useful when using paper ter-
                 minals).
       ^Y        Restore last item removed from line. (Yank item back  to  the
                 line.)
       ^L        Line feed and print current line.
       M-^L      Clear the screen.
       ^@        (Null character) Set mark.
       M-space   (Meta space) Set mark.
       ^J        (New line) Execute the current line.
       ^M        (Return) Execute the current line.
       eof       End-of-file  character,  normally ^D, is processed as an End-
                 of-file only if the current line is null.
       ^P        Fetch previous command.  Each time ^P is entered the previous
                 command  back  in time is accessed.  Moves back one line when
                 not on the first line of a multi-line command.
       M-[A      If the cursor is at the end of the line, it is equivalent  to
                 ^R with string set to the contents of the current line.  Oth-
                 erwise, it is equivalent to ^P.
       M-<       Fetch the least recent (oldest) history line.
       M->       Fetch the most recent (youngest) history line.
       ^N        Fetch next command line.  Each time ^N is  entered  the  next
                 command line forward in time is accessed.
       M-[B      Equivalent to ^N.
       ^Rstring  Reverse search history for a previous command line containing
                 string.  If a parameter of zero is given, the search is  for-
                 ward.   String is terminated by a 'RETURN' or 'NEW LINE'.  If
                 string is preceded by a ^, the matched line must  begin  with
                 string.   If  string  is  omitted, then the next command line
                 containing the most recent string is accessed.  In this  case
                 a parameter of zero reverses the direction of the search.
       ^O        Operate  -  Execute  the current line and fetch the next line
                 relative to current line from the history file.
       M-digits  (Escape) Define numeric parameter, the digits are taken as  a
                 parameter  to  the  next command.  The commands that accept a
                 parameter are ^F, ^B, erase, ^C, ^D, ^K, ^R, ^P, ^N, ^], M-.,
                 M-^], M-_, M-=, M-b, M-c, M-d, M-f, M-h, M-l and M-^H.
       M-letter  Soft-key  -  Your  alias list is searched for an alias by the
                 name _letter and if an alias of this  name  is  defined,  its
                 value  will  be inserted on the input queue.  The letter must
                 not be one of the above meta-functions.
       M-[letter Soft-key - Your alias list is searched for an  alias  by  the
                 name  __letter  and  if an alias of this name is defined, its
                 value will be inserted on the input queue.  This can be  used
                 to program function keys on many terminals.
       M-.       The  last  word  of  the  previous command is inserted on the
                 line.  If preceded by a numeric parameter, the value of  this
                 parameter  determines  which  word  to insert rather than the
                 last word.
       M-_       Same as M-..
       M-*       Attempt file name generation on the current word.  An  aster-
                 isk is appended if the word doesn't match any file or contain
                 any special pattern characters.
       M-ESC     Command or file name completion as described above.
       ^I tab    Attempts command or file name completion as described  above.
                 If a partial completion occurs, repeating this will behave as
                 if M-= were entered.  If no match is found or  entered  after
                 space, a tab is inserted.
       M-=       If not preceded by a numeric parameter, it generates the list
                 of matching  commands  or  file  names  as  described  above.
                 Otherwise,  the word under the cursor is replaced by the item
                 corresponding to the value of the numeric parameter from  the
                 most  recently generated command or file list.  If the cursor
                 is not on a word, it is inserted instead.
       ^U        Multiply parameter of next command by 4.
       \         Escape next character.  Editing characters, the user's erase,
                 kill  and  interrupt (normally ^?)  characters may be entered
                 in a command line or in a search string if preceded by  a  \.
                 The \ removes the next character's editing features (if any).
       M-^V      Display version of the shell.
       M-#       If the line does not begin with a #, a # is inserted  at  the
                 beginning  of  the line and after each new-line, and the line
                 is entered.  This causes a comment to be inserted in the his-
                 tory file.  If the line begins with a #, the # is deleted and
                 one # after each new-line is also deleted.

   Vi Editing Mode.
       There are two typing modes.  Initially, when you enter  a  command  you
       are in the input mode.  To edit, the user enters control mode by typing
       ESC (033) and moves the cursor to the point needing correction and then
       inserts  or  deletes  characters or words as needed.  Most control com-
       mands accept an optional repeat count prior to the command.

       When in vi mode on most  systems,  canonical  processing  is  initially
       enabled  and the command will be echoed again if the speed is 1200 baud
       or greater and it contains any control characters or less than one sec-
       ond has elapsed since the prompt was printed.  The ESC character termi-
       nates canonical processing for the remainder of  the  command  and  the
       user  can then modify the command line.  This scheme has the advantages
       of canonical processing with the type-ahead echoing of raw mode.

       If the option viraw is also set, the terminal will always have  canoni-
       cal processing disabled.  This mode is implicit for systems that do not
       support two alternate end of line delimiters, and may  be  helpful  for
       certain terminals.

        Input Edit Commands
              By default the editor is in input mode.
              erase     (User  defined  erase character as defined by the stty
                        command, usually ^H or #.)  Delete previous character.
              ^W        Delete  the  previous  blank  separated word.  On some
                        systems the viraw option may be required for  this  to
                        work.
              eof       As the first character of the line causes the shell to
                        terminate unless the ignoreeof option is set.   Other-
                        wise this character is ignored.
              lnext     (User defined literal next character as defined by the
                        stty(1) or ^V if not defined.)  Removes the next char-
                        acter's  editing  features  (if any).  On some systems
                        the viraw option may be required for this to work.
              \         Escape the next erase or kill character.
              ^I tab    Attempts command or file name completion as  described
                        above and returns to input mode.  If a partial comple-
                        tion occurs, repeating this will behave as if  =  were
                        entered  from  control  mode.  If no match is found or
                        entered after space, a tab is inserted.
        Motion Edit Commands
              These commands will move the cursor.
              [count]l  Cursor forward (right) one character.
              [count][C Cursor forward (right) one character.
              [count]w  Cursor forward one alpha-numeric word.
              [count]W  Cursor to the beginning of the next word that  follows
                        a blank.
              [count]e  Cursor to end of word.
              [count]E  Cursor to end of the current blank delimited word.
              [count]h  Cursor backward (left) one character.
              [count][D Cursor backward (left) one character.
              [count]b  Cursor backward one word.
              [count]B  Cursor to preceding blank separated word.
              [count]|  Cursor to column count.
              [count]fc Find the next character c in the current line.
              [count]Fc Find the previous character c in the current line.
              [count]tc Equivalent to f followed by h.
              [count]Tc Equivalent to F followed by l.
              [count];  Repeats  count  times,  the last single character find
                        command, f, F, t, or T.
              [count],  Reverses the last single character find command  count
                        times.
              0         Cursor to start of line.
              ^         Cursor to start of line.
              [H        Cursor to first non-blank character in line.
              $         Cursor to end of line.
              [Y        Cursor to end of line.
              %         Moves  to balancing (, ), {, }, [, or ].  If cursor is
                        not on one of the above characters, the  remainder  of
                        the  line  is searched for the first occurrence of one
                        of the above characters first.
        Search Edit Commands
              These commands access your command history.
              [count]k  Fetch previous command.  Each time k  is  entered  the
                        previous command back in time is accessed.
              [count]-  Equivalent to k.
              [count][A If  cursor  is at the end of the line it is equivalent
                        to / with string^set to the contents  of  the  current
                        line.  Otherwise, it is equivalent to k.
              [count]j  Fetch  next  command.  Each time j is entered the next
                        command forward in time is accessed.
              [count]+  Equivalent to j.
              [count][B Equivalent to j.
              [count]G  The command number count is fetched.  The  default  is
                        the least recent history command.
              /string   Search backward through history for a previous command
                        containing string.  String is terminated by a 'RETURN'
                        or  'NEW LINE'.   If  string  is  preceded by a ^, the
                        matched line must begin with  string.   If  string  is
                        null, the previous string will be used.
              ?string   Same  as  /  except that search will be in the forward
                        direction.
              n         Search for next match of the last pattern to  /  or  ?
                        commands.
              N         Search  for  next match of the last pattern to / or ?,
                        but in reverse direction.
        Text Modification Edit Commands
              These commands will modify the line.
              a         Enter input mode and  enter  text  after  the  current
                        character.
              A         Append text to the end of the line.  Equivalent to $a.
              [count]cmotion
              c[count]motion
                        Delete current character through  the  character  that
                        motion  would move the cursor to and enter input mode.
                        If motion is c, the entire line will  be  deleted  and
                        input mode entered.
              C         Delete  the  current character through the end of line
                        and enter input mode.  Equivalent to c$.
              S         Equivalent to cc.
              [count]s  Replace characters under the cursor in input mode.
              D         Delete the current character through the end of  line.
                        Equivalent to d$.
              [count]dmotion
              d[count]motion
                        Delete  current  character  through the character that
                        motion would move to.  If motion is  d  ,  the  entire
                        line will be deleted.
              i         Enter  input  mode  and insert text before the current
                        character.
              I         Insert text before the beginning of the line.  Equiva-
                        lent to 0i.
              [count]P  Place  the  previous text modification before the cur-
                        sor.
              [count]p  Place the previous text modification after the cursor.
              R         Enter  input mode and replace characters on the screen
                        with characters you type overlay fashion.
              [count]rc Replace the count character(s) starting at the current
                        cursor position with c, and advance the cursor.
              [count]x  Delete current character.
              [count]X  Delete preceding character.
              [count].  Repeat the previous text modification command.
              [count]~  Invert  the case of the count character(s) starting at
                        the current cursor position and advance the cursor.
              [count]_  Causes the count word of the previous  command  to  be
                        appended  and  input  mode  entered.  The last word is
                        used if count is omitted.
              *         Causes an * to be appended to  the  current  word  and
                        file name generation attempted.  If no match is found,
                        it rings the bell.  Otherwise, the word is replaced by
                        the matching pattern and input mode is entered.
              \         Command or file name completion as described above.
        Other Edit Commands
              Miscellaneous commands.
              [count]ymotion
              y[count]motion
                        Yank  current  character through character that motion
                        would move the cursor to and puts them into the delete
                        buffer.  The text and cursor are unchanged.
              yy        Yanks the entire line.
              Y         Yanks  from  current position to end of line.  Equiva-
                        lent to y$.
              u         Undo the last text modifying command.
              U         Undo all the text modifying commands performed on  the
                        line.
              [count]v  Returns  the  command hist -e ${VISUAL:-${EDITOR:-vi}}
                        count in the input buffer.  If count is omitted,  then
                        the current line is used.
              ^L        Line  feed and print current line.  Has effect only in
                        control mode.
              ^J        (New line) Execute the  current  line,  regardless  of
                        mode.
              ^M        (Return) Execute the current line, regardless of mode.
              #         If the first character of the command  is  a  #,  then
                        this  command deletes this # and each # that follows a
                        newline.  Otherwise, sends the line after inserting  a
                        #  in  front  of each line in the command.  Useful for
                        causing the current line to be inserted in the history
                        as  a  comment  and  uncommenting previously commented
                        commands in the history file.
              [count]=  If count is not specified, it generates  the  list  of
                        matching  commands  or  file names as described above.
                        Otherwise, the word under the the cursor  is  replaced
                        by  the  count  item  from the most recently generated
                        command or file list.  If the cursor is not on a word,
                        it is inserted instead.
              @letter   Your  alias  list is searched for an alias by the name
                        _letter and if an alias of this name is  defined,  its
                        value will be inserted on the input queue for process-
                        ing.
              ^V        Display version of the shell.

   Built-in Commands.
       The following  simple-commands  are  executed  in  the  shell  process.
       Input/Output redirection is permitted.  Unless otherwise indicated, the
       output is written on file descriptor 1 and the exit status, when  there
       is  no syntax error, is zero.  Except for :, true, false, echo, newgrp,
       and login, all built-in commands accept -- to indicate end of  options.
       They  also  interpret  the option --man as a request to display the man
       page onto standard error and -?  as a help request which prints a usage
       message  on standard error.  Commands that are preceded by one or two +
       symbols are special built-in commands and are treated specially in  the
       following ways:
       1.     Variable assignment lists preceding the command remain in effect
              when the command completes.
       2.     I/O redirections are processed after variable assignments.
       3.     Errors cause a script that contains them to abort.
       4.     They are not valid function names.
       5.     Words following a command preceded by ++ that are in the  format
              of  a  variable assignment are expanded with the same rules as a
              variable assignment.  This means that tilde substitution is per-
              formed after the = sign and field splitting and file name gener-
              ation are not performed.  These are  called  declaration  built-
              ins.

       + : [ arg ... ]
              The command only expands parameters.

       + . name [ arg ... ]
              If  name  is  a function defined with the function name reserved
              word syntax, the function is executed in the current environment
              (as  if  it had been defined with the name() syntax.)  Otherwise
              if name refers to a file, the file is read in its  entirety  and
              the commands are executed in the current shell environment.  The
              search path specified by PATH is used to find the directory con-
              taining  the  file.  If any arguments arg are given, they become
              the positional parameters while processing the  .   command  and
              the original positional parameters are restored upon completion.
              Otherwise the positional parameters  are  unchanged.   The  exit
              status is the exit status of the last command executed.

       ++ alias [ -ptx ]  [ name[ =value  ] ] ...
              alias  with  no arguments prints the list of aliases in the form
              name=value on standard output.  The -p option  causes  the  word
              alias  to  be  inserted before each one.  When one or more argu-
              ments are given, an alias is defined for each name  whose  value
              is  given.  A trailing space in value causes the next word to be
              checked for alias substitution.  The obsolete -t option is  used
              to  set  and list tracked aliases.  The value of a tracked alias
              is the full pathname corresponding to the given name.  The value
              becomes  undefined when the value of PATH is reset but the alias
              remains tracked.  Without the -t option, for each  name  in  the
              argument list for which no value is given, the name and value of
              the alias is printed.  The obsolete -x  option  has  no  effect.
              The  exit  status  is non-zero if a name is given, but no value,
              and no alias has been defined for the name.

       bg [ job... ]
              This command is only on systems that support job control.   Puts
              each  specified job into the background.  The current job is put
              in the background if job is  not  specified.   See  Jobs  for  a
              description of the format of job.

       + break [ n ]
              Exit  from  the  enclosing for, while, until, or select loop, if
              any.  If n is specified, then break n levels.

       builtin [ -ds ] [ -f file ] [ name ... ]
              If name is not specified, and no -f  option  is  specified,  the
              built-ins  are printed on standard output.  The -s option prints
              only the special built-ins.  Otherwise, each name represents the
              pathname  whose basename is the name of the built-in.  The entry
              point function name is determined by prepending b_ to the built-
              in  name.  The ISO C/C++ prototype is b_mycommand(int argc, char
              *argv[], void *context) for the builtin command mycommand  where
              argv  is  array  an  of argc elements and context is an optional
              pointer to a Shell_t structure as described in <ast/shell.h>.
              Special built-ins cannot be bound to a pathname or deleted.  The
              -d  option deletes each of the given built-ins.  On systems that
              support dynamic loading, the -f option names  a  shared  library
              containing  the  code  for built-ins.  The shared library prefix
              and/or suffix, which depend on the system, can be omitted.  Once
              a library is loaded, its symbols become available for subsequent
              invocations of builtin.  Multiple  libraries  can  be  specified
              with separate invocations of the builtin command.  Libraries are
              searched in the reverse order in which they are specified.  When
              a  library  is  loaded,  it  looks for a function in the library
              whose name is lib_init() and invokes this function with an argu-
              ment of 0.

       cd [ -LP ] [ arg ]
       cd [ -LP ] old new
              This  command  can be in either of two forms.  In the first form
              it changes the current directory to arg.  If arg is - the direc-
              tory  is  changed to the previous directory.  The shell variable
              HOME is the default arg.  The variable PWD is set to the current
              directory.   The  shell  variable CDPATH defines the search path
              for the directory containing arg.  Alternative  directory  names
              are separated by a colon (:).  The default path is <null> (spec-
              ifying the current directory).  Note that the current  directory
              is  specified  by a null path name, which can appear immediately
              after the equal sign or between the  colon  delimiters  anywhere
              else  in  the path list.  If arg begins with a / then the search
              path is not used.  Otherwise, each  directory  in  the  path  is
              searched for arg.
              The  second form of cd substitutes the string new for the string
              old in the current directory name, PWD, and tries to  change  to
              this new directory.
              By default, symbolic link names are treated literally when find-
              ing the directory name.  This is equivalent to  the  -L  option.
              The  -P  option causes symbolic links to be resolved when deter-
              mining the directory.  The last instance of -L or -P on the com-
              mand line determines which method is used.
              The cd command may not be executed by rksh.  rksh93.

       command [ -pvxV ] name [ arg ... ]
              Without  the  -v  or  -V options, command executes name with the
              arguments given by arg.  The -p option causes a default path  to
              be  searched  rather  than the one defined by the value of PATH.
              Functions will not be searched for when finding name.  In  addi-
              tion,  if name refers to a special built-in, none of the special
              properties associated with the leading daggers will be  honored.
              (For  example, the predefined alias redirect=?command exec? pre-
              vents a script from terminating when an invalid  redirection  is
              given.)   With  the -x option, if command execution would result
              in a failure because there are too many arguments, errno  E2BIG,
              the  shell will invoke command name multiple times with a subset
              of the arguments on each invocation.  Arguments that occur prior
              to  the  first word that expands to multiple arguments and after
              the last word that expands to multiple arguments will be  passed
              on each invocation.  The exit status will be the maximum invoca-
              tion exit status.  With the -v option, command is equivalent  to
              the  built-in  whence  command  described  below.  The -V option
              causes command to act like whence -v.

       + continue [ n ]
              Resume the next iteration of the enclosing for, while, until, or
              select loop.  If n is specified, then resume at the n-th enclos-
              ing loop.

       disown [ job... ]
              Causes the shell not to send a HUP signal to each given job,  or
              all  active  jobs  if  job is omitted, when a login shell termi-
              nates.

       echo [ arg ... ]
              When the first arg does not begin with a  -,  and  none  of  the
              arguments  contain  a  \, then echo prints each of its arguments
              separated by a space and terminated by a  new-line.   Otherwise,
              the  behavior  of  echo  is system dependent and print or printf
              described below should be  used.   See  echo(1)  for  usage  and
              description.

       ++ enum [ -i  ] type[=(value ...) ]
              Creates a declaration command named type that is an integer type
              that allows one of the specified values  as  enumeration  names.
              If  =(value ...)  is omitted, then type must be an indexed array
              variable with at least two elements and  the  values  are  taken
              from  this  array  variable.   If -i is specified the values are
              case insensitive.

       + eval [ arg ... ]
              The arguments are read as input to the shell and  the  resulting
              command(s) executed.

       + exec [ -c ] [ -a name ] [ arg ... ]
              If  arg is given, the command specified by the arguments is exe-
              cuted in place of this shell without  creating  a  new  process.
              The -c option causes the environment to be cleared before apply-
              ing variable assignments associated with  the  exec  invocation.
              The  -a  option causes name rather than the first arg, to become
              argv[0] for the new process.  Input/output arguments may  appear
              and affect the current process.  If arg is not given, the effect
              of this command is to modify file descriptors as  prescribed  by
              the  input/output  redirection  list.   In  this  case, any file
              descriptor numbers greater than 2  that  are  opened  with  this
              mechanism are closed when invoking another program.

       + exit [ n ]
              Causes  the  shell  to exit with the exit status specified by n.
              The value will be the least significant 8 bits of the  specified
              status.   If  n  is omitted, then the exit status is that of the
              last command executed.  An end-of-file will also cause the shell
              to  exit  except for a shell which has the ignoreeof option (see
              set below) turned on.

       ++ export [ -p ] [ name[=value] ] ...
              If name is not given, the names and values of each variable with
              the  export  attribute  are  printed with the values quoted in a
              manner that allows them to be re-input.  The  -p  option  causes
              the  word export to be inserted before each one.  Otherwise, the
              given names are marked for automatic export to  the  environment
              of subsequently-executed commands.

       false  Does nothing, and exits 1. Used with until for infinite loops.

       fg [ job... ]
              This  command is only on systems that support job control.  Each
              job specified is brought to the foreground and waited for in the
              specified order.  Otherwise, the current job is brought into the
              foreground.  See Jobs for a description of the format of job.

       getconf [ name [ pathname ] ]
              Prints the current value of the configuration parameter given by
              name.   The  configuration  parameters  are  defined by the IEEE
              POSIX 1003.1 and IEEE POSIX 1003.2 standards.  (See  pathconf(2)
              and  sysconf(2).)  The pathname argument is required for parame-
              ters whose value depends on the location in the file system.  If
              no  arguments  are given, getconf prints the names and values of
              the current configuration parameters.  The pathname  /  is  used
              for each of the parameters that requires pathname.

       getopts [  -a name ] optstring vname [ arg ... ]
              Checks arg for legal options.  If arg is omitted, the positional
              parameters are used.  An option argument begins with a + or a -.
              An  option not beginning with + or - or the argument -- ends the
              options.  Options beginning with + are only recognized when opt-
              string  begins  with  a  +.  optstring contains the letters that
              getopts recognizes.  If a letter is followed by a :, that option
              is  expected  to have an argument.  The options can be separated
              from the argument by blanks.  The option -?  causes  getopts  to
              generate a usage message on standard error.  The -a argument can
              be used to specify the name to use for the usage message,  which
              defaults to $0.
              getopts  places  the next option letter it finds inside variable
              vname each time it  is  invoked.   The  option  letter  will  be
              prepended  with  a + when arg begins with a +.  The index of the
              next arg is stored in OPTIND.  The option argument, if any, gets
              stored in OPTARG.
              A  leading  : in optstring causes getopts to store the letter of
              an invalid option in OPTARG, and to  set  vname  to  ?   for  an
              unknown option and to : when a required option argument is miss-
              ing.  Otherwise, getopts prints an error message.  The exit sta-
              tus is non-zero when there are no more options.
              There is no way to specify any of the options :, +, -, ?, [, and
              ].  The option # can only be specified as the first option.

       hist [ -e ename  ] [ -nlr ] [ first [ last ] ]
       hist -s  [ old=new ] [ command ]
              In the first form, a range of commands from  first  to  last  is
              selected  from the last HISTSIZE commands that were typed at the
              terminal.  The arguments first and last may be  specified  as  a
              number  or  as  a  string.   A string is used to locate the most
              recent command starting with the given string.  A negative  num-
              ber  is used as an offset to the current command number.  If the
              -l option is selected, the commands are listed on standard  out-
              put.   Otherwise,  the editor program ename is invoked on a file
              containing these keyboard commands.  If ename is  not  supplied,
              then the value of the variable HISTEDIT is used.  If HISTEDIT is
              not set, then FCEDIT (default /bin/ed) is used  as  the  editor.
              When  editing  is complete, the edited command(s) is executed if
              the changes have been saved.  If last is not specified, then  it
              will be set to first.  If first is not specified, the default is
              the previous command for  editing  and  -16  for  listing.   The
              option  -r  reverses the order of the commands and the option -n
              suppresses command numbers when listing.  In  the  second  form,
              command  is interpreted as first described above and defaults to
              the last command executed.  The resulting  command  is  executed
              after the optional substitution old=new is performed.

       jobs [ -lnp ] [ job ... ]
              Lists  information  about  each given job; or all active jobs if
              job is omitted.  The -l option lists process ids in addition  to
              the  normal  information.  The -n option only displays jobs that
              have stopped or exited  since  last  notified.   The  -p  option
              causes  only  the  process  group  to be listed.  See Jobs for a
              description of the format of job.

       kill [ -s signame ] job ...
       kill [ -n signum ] job ...
       kill -l [ sig ... ]
              Sends either the TERM (terminate) signal or the specified signal
              to the specified jobs or processes.  Signals are either given by
              number with the -n option or by name  with  the  -s  option  (as
              given  in  <signal.h>,  stripped  of the prefix ''SIG'' with the
              exception that SIGCLD is named CHLD).  For backward  compatibil-
              ity,  the  n  and s can be omitted and the number or name placed
              immediately after the -.  If the signal being sent is TERM (ter-
              minate)  or HUP (hangup), then the job or process will be sent a
              CONT (continue) signal if it is stopped.  The argument  job  can
              be  the  process  id of a process that is not a member of one of
              the active jobs.  See Jobs for a description of  the  format  of
              job.   In  the third form, kill -l, if sig is not specified, the
              signal names are listed.  Otherwise, for  each  sig  that  is  a
              name,  the  corresponding signal number is listed.  For each sig
              that is a number, the signal name  corresponding  to  the  least
              significant 8 bits of sig is listed.

       let arg ...
              Each  arg  is  a separate arithmetic expression to be evaluated.
              See Arithmetic Evaluation above, for a description of arithmetic
              expression evaluation.
              The exit status is 0 if the value of the last expression is non-
              zero, and 1 otherwise.

       + newgrp [ arg ... ]
              Equivalent to exec /bin/newgrp arg ....

       print [ -CRenprsv ] [ -u unit] [ -f format ] [ arg ... ]
              With no options or with option - or --, each arg is  printed  on
              standard  output.   The  -f  option  causes  the arguments to be
              printed as described by printf.  In this case, any e,  n,  r,  R
              options  are  ignored.   Otherwise, unless the -C, -R, -r, or -v
              are specified, the following escape conventions will be applied:
              \a     The alert character (ascii 07).
              \b     The backspace character (ascii 010).
              \c     Causes print to end without processing more arguments and
                     not adding a new-line.
              \f     The formfeed character (ascii 014).
              \n     The new-line character (ascii 012).
              \r     The carriage return character (ascii 015).
              \t     The tab character (ascii 011).
              \v     The vertical tab character (ascii 013).
              \E     The escape character (ascii 033).
              \\     The backslash character \.
              \0x    The character defined by  the  1,  2,  or  3-digit  octal
                     string given by x.

              The  -R  option  will print all subsequent arguments and options
              other than -n.  The -e causes the above escape conventions to be
              applied.   This is the default behavior.  It reverses the effect
              of an earlier -r.  The -p option  causes  the  arguments  to  be
              written  onto the pipe of the process spawned with |& instead of
              standard output.  The -v option treats each arg  as  a  variable
              name  and  writes  the  value  in  the printf %B format.  The -C
              option treats each arg as a variable name and writes  the  value
              in the printf %#B format.  The -s option causes the arguments to
              be written onto the history file  instead  of  standard  output.
              The -u option can be used to specify a one digit file descriptor
              unit number unit on  which  the  output  will  be  placed.   The
              default is 1.  If the option -n is used, no new-line is added to
              the output.

       printf format [ arg ... ]
              The arguments arg are printed on standard output  in  accordance
              with  the  ANSI-C  formatting  rules  associated with the format
              string format.  If the number of arguments exceeds the number of
              format  specifications,  the  format  string is reused to format
              remaining arguments.  The following extensions can also be used:
              %b     A  %b  format  can  be used instead of %s to cause escape
                     sequences in the corresponding  arg  to  be  expanded  as
                     described in print.
              %B     A %B option causes each of the arguments to be treated as
                     variable names and the binary value of variable  will  be
                     printed.  The alternate flag # causes a compound variable
                     to be output on a single line.  This is most  useful  for
                     compound variables and variables whose attribute is -b.
              %H     A %H format can be used instead of %s to cause characters
                     in arg that are special in HTML and XML to be  output  as
                     their entity name.
              %P     A  %P format can be used instead of %s to cause arg to be
                     interpreted as an  extended  regular  expression  and  be
                     printed as a shell pattern.
              %R     A  %R format can be used instead of %s to cause arg to be
                     interpreted as a shell pattern and to be  printed  as  an
                     extended regular expression.
              %q     A  %q  format  can  be  used  instead  of %s to cause the
                     resulting string to be quoted in a  manner  than  can  be
                     reinput to the shell.
              %(date-format)T
                     A  %(date-format)T format can be use to treat an argument
                     as a date/time string and to format the date/time accord-
                     ing  to  the  date-format as defined for the date(1) com-
                     mand.
              %Z     A %Z format will output a byte whose value is 0.
              %d     The precision field of the %d format can be followed by a
                     .  and the output base.  In this case, the # flag charac-
                     ter causes base# to be prepended.
              #      The # flag when used with the d specifier without an out-
                     put  base, causes the output to be displayed in thousands
                     units with one of the suffixes k M G T P  E  to  indicate
                     the  unit.   The  #  flag  when used with the i specifier
                     causes the output to be displayed in 1024 with one of the
                     suffixes Ki Mi Gi Ti Pi Ei to indicate the unit.
              =      The = flag has been added to center the output within the
                     specified field width.

       pwd [ -LP ]
              Outputs the value of the  current  working  directory.   The  -L
              option is the default; it prints the logical name of the current
              directory.  If the -P option is given, all  symbolic  links  are
              resolved  from  the  name.  The last instance of -L or -P on the
              command line determines which method is used.

       read [ -ACprsv ] [ -d delim] [ -n n] [ [ -N n] [ [  -t  timeout]  [  -u
       unit] [ vname?prompt ] [ vname ... ]
              The shell input mechanism.  One line is read and  is  broken  up
              into  fields  using  the  characters  in IFS as separators.  The
              escape character, \, is used to remove any special  meaning  for
              the  next  character  and  for line continuation.  The -d option
              causes the read to continue to  the  first  character  of  delim
              rather  than  new-line.  The -n option causes at most n bytes to
              read rather a full line but will return when reading from a slow
              device  as soon as any characters have been read.  The -N option
              causes exactly n to be  read  unless  an  end-of-file  has  been
              encountered  or the read times out because of the -t option.  In
              raw mode, -r, the \ character is  not  treated  specially.   The
              first  field is assigned to the first vname, the second field to
              the second vname, etc., with leftover  fields  assigned  to  the
              last vname.  When vname has the binary attribute and -n or -N is
              specified, the bytes that are read are stored directly into  the
              variable.   If  the -v is specified, then the value of the first
              vname will be used as a default value when reading from a termi-
              nal device.  The -A option causes the variable vname to be unset
              and each field that is read to be stored in successive  elements
              of  the  indexed array vname.  The -C option causes the variable
              vname to be read as a compound variable.  Blanks will be ignored
              when  finding  the  beginning  open  parenthesis.  The -p option
              causes the input line to be taken from the input pipe of a  pro-
              cess  spawned  by  the  shell  using  |&.   If  the -s option is
              present, the input will be saved as a  command  in  the  history
              file.   The  option  -u  can be used to specify a one digit file
              descriptor unit unit to read from.  The file descriptor  can  be
              opened  with  the  exec  special  built-in command.  The default
              value of unit n is 0.  The option -t is used to specify a  time-
              out  in  seconds when reading from a terminal or pipe.  If vname
              is omitted, then REPLY is used as the default vname.  An end-of-
              file  with the -p option causes cleanup for this process so that
              another can be spawned.  If the first argument contains a ?, the
              remainder  of  this  word  is used as a prompt on standard error
              when the shell is interactive.  The exit status is 0  unless  an
              end-of-file is encountered or read has timed out.

       ++ readonly [ -p ] [ vname[=value] ] ...
              If  vname  is  not  given, the names and values of each variable
              with the readonly attribute is printed with the values quoted in
              a  manner  that  allows  them  to be re-inputted.  The -p option
              causes the word readonly to be inserted before each one.  Other-
              wise,  the given vnames are marked readonly and these names can-
              not be changed by subsequent assignment.  When defining a  type,
              if the value of a readonly sub-variable is not defined the value
              is required when creating each instance.

       + return [ n ]
              Causes a shell function or .  script to return to  the  invoking
              script  with  the exit status specified by n.  The value will be
              the least significant 8 bits of the specified status.  If  n  is
              omitted, then the return status is that of the last command exe-
              cuted.  If return is invoked while not in  a  function  or  a  .
              script, then it behaves the same as exit.

       +  set  [  ?BCGabefhkmnoprstuvx ] [ ?o [ option ] ] ... [ ?A vname ]  [
       arg ... ]
              The options for this command have meaning as follows:
              -A      Array  assignment.   Unset the variable vname and assign
                      values sequentially from the arg list.  If +A  is  used,
                      the variable vname is not unset first.
              -B      Enable  brace  pattern  field  generation.   This is the
                      default behavior.
              -B      Enable brace group expansion.  On by default.
              -C      Prevents redirection > from truncating  existing  files.
                      Files  that are created are opened with the O_EXCL mode.
                      Requires >| to truncate a file when turned on.
              -G      Causes the pattern ** by itself to match files and  zero
                      or  more  directories  and sub-directories when used for
                      file name generation.  If followed by a / only  directo-
                      ries and sub-directories are matched.
              -a      All  subsequent variables that are defined are automati-
                      cally exported.
              -b      Prints job completion messages as soon as  a  background
                      job  changes  state  rather  than  waiting  for the next
                      prompt.
              -e      Unless contained in a || or && command, or  the  command
                      following  an  if  while  or  until  command  or  in the
                      pipeline following !, if a command has a  non-zero  exit
                      status,  execute  the  ERR trap, if set, and exit.  This
                      mode is disabled while reading profiles.
              -f      Disables file name generation.
              -h      Each command becomes a tracked alias when first  encoun-
                      tered.
              -k      (Obsolete). All variable assignment arguments are placed
                      in the environment for a command, not  just  those  that
                      precede the command name.
              -m      Background jobs will run in a separate process group and
                      a line will print upon completion.  The exit  status  of
                      background jobs is reported in a completion message.  On
                      systems with job control, this option is turned on auto-
                      matically for interactive shells.
              -n      Read  commands  and check them for syntax errors, but do
                      not execute them.  Ignored for interactive shells.
              -o      The following argument  can  be  one  of  the  following
                      option names:
                      allexport
                              Same as -a.
                      errexit Same as -e.
                      bgnice  All background jobs are run at a lower priority.
                              This is the default mode.
                      braceexpand
                              Same as -B.
                      emacs   Puts you in an emacs style  in-line  editor  for
                              command entry.
                      globstar
                              Same as -G.
                      gmacs   Puts  you  in  a  gmacs style in-line editor for
                              command entry.
                      ignoreeof
                              The shell will not  exit  on  end-of-file.   The
                              command exit must be used.
                      keyword Same as -k.
                      markdirs
                              All  directory  names  resulting  from file name
                              generation have a trailing / appended.
                      monitor Same as -m.
                      multiline
                              The built-in editors will use multiple lines  on
                              the  screen  for  lines that are longer than the
                              width of the screen.  This may not work for  all
                              terminals.
                      noclobber
                              Same as -C.
                      noexec  Same as -n.
                      noglob  Same as -f.
                      nolog   Do  not save function definitions in the history
                              file.
                      notify  Same as -b.
                      nounset Same as -u.
                      pipefail
                              A pipeline will not complete  until  all  compo-
                              nents  of  the  pipeline have completed, and the
                              return value will be the value of the last  non-
                              zero  command  to fail or zero if no command has
                              failed.
                      showme  When enabled, simple commands or pipelines  pre-
                              ceded by a semicolon (;) will be displayed as if
                              the xtrace option were enabled but will  not  be
                              executed.   Otherwise,  the  leading  ;  will be
                              ignored.
                      privileged
                              Same as -p.
                      verbose Same as -v.
                      trackall
                              Same as -h.
                      vi      Puts you in insert mode of a  vi  style  in-line
                              editor  until  you hit the escape character 033.
                              This puts you in control mode.  A  return  sends
                              the line.
                      viraw   Each character is processed as it is typed in vi
                              mode.
                      xtrace  Same as -x.
                      If no option name is supplied, then the  current  option
                      settings are printed.
              -p      Disables  processing of the $HOME/.profile file and uses
                      the file /etc/suid_profile  instead  of  the  ENV  file.
                      This  mode is on whenever the effective uid (gid) is not
                      equal to the real uid (gid).  Turning  this  off  causes
                      the  effective uid and gid to be set to the real uid and
                      gid.
              -r      Enables the restricted shell.   This  option  cannot  be
                      unset once set.
              -s      Sort the positional parameters lexicographically.
              -t      (Obsolete).   Exit  after reading and executing one com-
                      mand.
              -u      Treat unset parameters as an error when substituting.
              -v      Print shell input lines as they are read.
              -x      Print commands and their arguments as they are executed.
              --      Do  not  change any of the options; useful in setting $1
                      to a value beginning with -.   If  no  arguments  follow
                      this option then the positional parameters are unset.

              As an obsolete feature, if the first arg is - then the -x and -v
              options are turned off and the next arg is treated as the  first
              argument.   Using  +  rather  than  - causes these options to be
              turned off.  These options can also be used upon  invocation  of
              the  shell.   The  current  set  of  options may be found in $-.
              Unless -A is specified, the remaining arguments  are  positional
              parameters  and  are  assigned,  in  order, to $1 $2 ....  If no
              arguments are given, then the names and values of all  variables
              are printed on the standard output.

       + shift [ n ]
              The  positional  parameters  from $n+1 ...  are renamed $1 ... ,
              default n is 1.  The parameter n can be any  arithmetic  expres-
              sion  that evaluates to a non-negative number less than or equal
              to $#.

       sleep seconds
              Suspends execution for the number of decimal  seconds  or  frac-
              tions of a second given by seconds.

       + trap [ -p ] [ action ] [ sig ] ...
              The  -p  option causes the trap action associated with each trap
              as specified by the arguments to  be  printed  with  appropriate
              quoting.   Otherwise,  action will be processed as if it were an
              argument to eval when the shell receives  signal(s)  sig.   Each
              sig can be given as a number or as the name of the signal.  Trap
              commands are executed in order of signal number.  Any attempt to
              set  a trap on a signal that was ignored on entry to the current
              shell is ineffective.  If action is omitted and the first sig is
              a  number,  or if action is -, then the trap(s) for each sig are
              reset to their original values.  If action is  the  null  string
              then  this signal is ignored by the shell and by the commands it
              invokes.  If sig is ERR then action will be executed whenever  a
              command has a non-zero exit status.  If sig is DEBUG then action
              will be executed before each command.  The variable  .sh.command
              will  contain  the  contents  of  the  current command line when
              action is running.  If the exit status of the trap is 2 the com-
              mand  will  not  be executed.  If the exit status of the trap is
              255 and inside a function or a dot script, the function  or  dot
              script  will return.  If sig is 0 or EXIT and the trap statement
              is executed inside the body of a function defined with the func-
              tion  name syntax, then the command action is executed after the
              function completes.  If sig is 0 or EXIT for a trap set  outside
              any  function  then  the command action is executed on exit from
              the shell.  If sig is KEYBD, then action will be executed  when-
              ever  a key is read while in emacs, gmacs, or vi mode.  The trap
              command with no arguments prints a list of  commands  associated
              with each signal number.

       An  exit  or  return without an argument in a trap action will preserve
       the exit status of the command that invoked the trap.

       true   Does nothing, and exits 0. Used with while for infinite loops.

       true   Does nothing, and exits 0. Used with while for infinite loops.

       ++ typeset [ ?ACHSflbnprtux ] [ ?EFLRXZi[n] ]  [ -T tname=(assign_list)
       ] [ -h str ] [ -a [type] ] [ vname[=value ]  ] ...
              Sets attributes and values for shell  variables  and  functions.
              When  invoked  inside  a function defined with the function name
              syntax, a new instance of the variable vname is created, and the
              variable's  value  and  type are restored when the function com-
              pletes.  The following list of attributes may be specified:
              -A     Declares vname to be an  associative  array.   Subscripts
                     are strings rather than arithmetic expressions.
              -C     causes each vname to be a compound variable.  value names
                     a compound variable it is copied into vname.   Otherwise,
                     it unsets each vname.
              -a     Declares vname to be an indexed array.  If type is speci-
                     fied, it must be the name of an enumeration type  created
                     with the enum command and it allows enumeration constants
                     to be used as subscripts.
              -E     Declares vname to be a double  precision  floating  point
                     number.   If n is non-zero, it defines the number of sig-
                     nificant figures that  are  used  when  expanding  vname.
                     Otherwise, ten significant figures will be used.
              -F     Declares  vname  to  be a double precision floating point
                     number.  If n is  non-zero,  it  defines  the  number  of
                     places after the decimal point that are used when expand-
                     ing vname.  Otherwise ten places after the decimal  point
                     will be used.
              -H     This  option  provides  UNIX to host-name file mapping on
                     non-UNIX machines.
              -L     Left justify and remove leading blanks from value.  If  n
                     is non-zero, it defines the width of the field, otherwise
                     it is determined by the  width  of  the  value  of  first
                     assignment.   When  the  variable  is  assigned to, it is
                     filled on the right with blanks or truncated,  if  neces-
                     sary,  to  fit  into  the field.  The -R option is turned
                     off.
              -R     Right justify and fill with leading blanks.  If n is non-
                     zero,  it defines the width of the field, otherwise it is
                     determined by the width of the value of first assignment.
                     The  field  is  left filled with blanks or truncated from
                     the end if the variable is reassigned.  The -L option  is
                     turned off.
              -S     When used within the assign_list of a type definition, it
                     causes the specified sub-variable to  be  shared  by  all
                     instances  of  the  type.   When  used  inside a function
                     defined with the function reserved  word,  the  specified
                     variables  will  have  function static scope.  Otherwise,
                     the variable is unset prior to processing the  assignment
                     list.
              -T     Creates  a type named by tname using the compound assign-
                     ment assign_list to tname.
              -X     Declares vname to be a double  precision  floating  point
                     number  and expands using the %a format of ISO-C99.  If n
                     is non-zero, it defines the number of  hex  digits  after
                     the  radix  point that is used when expanding vname.  The
                     default is 10.
              -Z     Right justify and fill with leading zeros  if  the  first
                     non-blank  character is a digit and the -L option has not
                     been set.  Remove leading zeros if the -L option is  also
                     set.   If  n  is  non-zero,  it  defines the width of the
                     field, otherwise it is determined by  the  width  of  the
                     value of first assignment.
              -f     The  names  refer  to function names rather than variable
                     names.  No assignments can be made  and  the  only  other
                     valid  options are -t, -u and -x.  The -t option turns on
                     execution tracing  for  this  function.   The  -u  option
                     causes  this  function to be marked undefined.  The FPATH
                     variable will be searched to find the function definition
                     when  the  function  is  referenced.  If no options other
                     than -f is specified, then the function  definition  will
                     be  displayed  on  standard  output.  If +f is specified,
                     then a line containing the function name  followed  by  a
                     shell comment containing the line number and path name of
                     the file where this function was defined, if any, is dis-
                     played.
              -b     The  variable  can hold any number of bytes of data.  The
                     data can be text or binary.  The value is represented  by
                     the  base64  encoding  of the data.  If -Z is also speci-
                     fied, the size in bytes of the data in the buffer will be
                     determined  by  the  size associated with the -Z.  If the
                     base64 string assigned results in more data, it  will  be
                     truncated.  Otherwise, it will be filled with bytes whose
                     value is zero.  The printf format %B can be used to  out-
                     put  the actual data in this buffer instead of the base64
                     encoding of the data.
              -h     Used within type definitions to add information when gen-
                     erating  information  about  the  sub-variable on the man
                     page.  It is ignored when used outside of a type  defini-
                     tion.   When  used  with -f the information is associated
                     with the corresponding discipline function.
              -i     Declares vname to be represented internally  as  integer.
                     The  right  hand side of an assignment is evaluated as an
                     arithmetic expression when assigning to an integer.  If n
                     is  non-zero, it defines the output arithmetic base, oth-
                     erwise the output base will be ten.
              -l     All upper-case characters are  converted  to  lower-case.
                     The upper-case option, -u, is turned off.
              -n     Declares  vname  to  be a reference to the variable whose
                     name is defined by the value of variable vname.  This  is
                     usually  used  to  reference a variable inside a function
                     whose name has been passed as an argument.
              -p     The name, attributes and values for the given vnames  are
                     written  on standard output in a form that can be used as
                     shell input.  If +p is specified, then the values are not
                     displayed.
              -r     The given vnames are marked readonly and these names can-
                     not be changed by subsequent assignment.
              -t     Tags the variables.  Tags are user definable and have  no
                     special meaning to the shell.
              -u     All  lower-case  characters  are converted to upper-case.
                     The lower-case option, -l, is turned off.
              -x     The given vnames are marked for automatic export  to  the
                     environment of subsequently-executed commands.  Variables
                     whose names contain a .  cannot be exported.

              The -i attribute cannot be specified along with -R, -L,  -Z,  or
              -f.

              Using + rather than - causes these options to be turned off.  If
              no vname arguments are given, a list of vnames  (and  optionally
              the values) of the variables is printed.  (Using + rather than -
              keeps the values from being  printed.)   The  -p  option  causes
              typeset followed by the option letters to be printed before each
              name rather than the names of the options.  If any option  other
              than  -p  is  given,  only those variables which have all of the
              given options are printed.  Otherwise, the vnames and attributes
              of all variables that have attributes are printed.

       ulimit [ -HSacdfmnpstv ] [ limit ]
              Set  or display a resource limit.  The available resource limits
              are listed below.  Many systems do not support one  or  more  of
              these  limits.   The  limit for a specified resource is set when
              limit is specified.  The value of limit can be a number  in  the
              unit specified below with each resource, or the value unlimited.
              The -H and -S options specify whether the hard limit or the soft
              limit  for  the  given  resource is set.  A hard limit cannot be
              increased once it is set.  A soft limit can be increased  up  to
              the  value  of the hard limit.  If neither the H nor S option is
              specified, the limit applies  to  both.   The  current  resource
              limit  is printed when limit is omitted.  In this case, the soft
              limit is printed unless H is  specified.   When  more  than  one
              resource  is  specified, then the limit name and unit is printed
              before the value.
              -a     Lists all of the current resource limits.
              -c     The number of 512-byte blocks on the size of core  dumps.
              -d     The number of K-bytes on the size of the data area.
              -f     The  number of 512-byte blocks on files that can be writ-
                     ten by the current process or by child  processes  (files
                     of any size may be read).
              -m     The number of K-bytes on the size of physical memory.
              -n     The number of file descriptors plus 1.
              -p     The number of 512-byte blocks for pipe buffering.
              -s     The number of K-bytes on the size of the stack area.
              -t     The number of CPU seconds to be used by each process.
              -v     The number of K-bytes for virtual memory.

              If no option is given, -f is assumed.

       umask [ -S ] [ mask ]
              The user file-creation mask is set to mask (see umask(2)).  mask
              can either be an octal number or a symbolic value  as  described
              in  chmod(1).  If a symbolic value is given, the new umask value
              is the complement of the result of applying mask to the  comple-
              ment  of the previous umask value.  If mask is omitted, the cur-
              rent value of the mask is printed.  The  -S  option  causes  the
              mode  to be printed as a symbolic value.  Otherwise, the mask is
              printed in octal.

       + unalias [ -a ] name ...
              The aliases given by the list of  names  are  removed  from  the
              alias list.  The -a option causes all the aliases to be unset.

       +unset [ -fnv ] vname ...
              The  variables given by the list of vnames are unassigned, i.e.,
              except  for  sub-variables  within  a  type,  their  values  and
              attributes  are erased.  For sub-variables of a type, the values
              are reset to the default value from the type definition.   Read-
              only  variables  cannot be unset.  If the -f option is set, then
              the names refer to function names.  If the  -v  option  is  set,
              then the names refer to variable names.  The -f option overrides
              -v.  If -n is set and name is a name reference, then  name  will
              be  unset  rather  than  the  variable  that it references.  The
              default is  equivalent  to  -v.   Unsetting  LINENO,  MAILCHECK,
              OPTARG, OPTIND, RANDOM, SECONDS, TMOUT, and _ removes their spe-
              cial meaning even if they are subsequently assigned to.

       wait [ job ... ]
              Wait for the specified job and report  its  termination  status.
              If  job  is not given, then all currently active child processes
              are waited for.  The exit status from this command  is  that  of
              the last process waited for if job is specified; otherwise it is
              zero.  See Jobs for a description of the format of job.

       whence [ -afpv ] name ...
              For each name, indicate how it would be interpreted if used as a
              command name.
              The  -v  option  produces  a more verbose report.  The -f option
              skips the search for functions.   The  -p  option  does  a  path
              search  for  name  even  if  name  is an alias, a function, or a
              reserved word.  The -p option turns off the -v option.   The  -a
              option  is  similar  to the -v option but causes all interpreta-
              tions of the given name to be reported.

   Invocation.
       If the shell is invoked by exec(2), and the first character of argument
       zero  ($0) is -, then the shell is assumed to be a login shell and com-
       mands are read from /etc/profile and then from either .profile  in  the
       current  directory or $HOME/.profile, if either file exists.  Next, for
       interactive shells, commands are read from the file named by performing
       parameter  expansion, command substitution, and arithmetic substitution
       on the value of the environment variable ENV if the  file  exists.   If
       the  -s  option  is  not  present and arg and a file by the name of arg
       exists, then it reads and executes  this  script.   Otherwise,  if  the
       first arg does not contain a /, a path search is performed on the first
       arg to determine the name of the script to  execute.   The  script  arg
       must have execute permission and any setuid and setgid settings will be
       ignored.  If the script is not found on the path, arg is  processed  as
       if  it named a built-in command or function.  Commands are then read as
       described below; the following options are  interpreted  by  the  shell
       when it is invoked:

       -D      Do  not execute the script, but output the set of double quoted
               strings preceded by a $.  These strings are needed  for  local-
               ization of the script to different locales.
       -E      Reads  the file named by the ENV variable or by $HOME/.kshrc if
               not defined after the profiles.
       -c        If the -c option is present, then commands are read from  the
                 first arg.  Any remaining arguments become positional parame-
                 ters starting at 0.
       -s        If the -s option is present or if no arguments  remain,  then
                 commands  are  read  from  the standard input.  Shell output,
                 except for the output of the Special Commands  listed  above,
                 is written to file descriptor 2.
       -i        If  the  -i option is present or if the shell input and error
                 output are attached to a terminal (as told by  tcgetattr(2)),
                 then this shell is interactive.  In this case TERM is ignored
                 (so that kill 0 does not kill an interactive shell) and  INTR
                 is  caught  and  ignored (so that wait is interruptible).  In
                 all cases, QUIT is ignored by the shell.
       -r        If the -r option is present, the shell is a restricted shell.
       -D        A  list of all double quoted strings that are preceded by a $
                 will be printed on standard output and the shell  will  exit.
                 This  set  of strings will be subject to language translation
                 when the locale is not C or POSIX.  No commands will be  exe-
                 cuted.

       -P        If  -P or -o profile is present, the shell is a profile shell
                 (see pfexec(1)).

       -R filename
                 The -R filename option is used to generate a cross  reference
                 database that can be used by a separate utility to find defi-
                 nitions and references for variables and commands.  The file-
                 name argument specifies the generated database. A script file
                 must be provided on the command line as well.

       The remaining options and arguments are described under the set command
       above.  An optional - as the first argument is ignored.

   Rksh Only.
       Rksh  is  used  to  set up login names and execution environments whose
       capabilities are more controlled than those of the standard shell.  The
       actions  of rksh are identical to those of ksh, except that the follow-
       ing are disallowed:
              Unsetting the restricted option.
              changing directory (see cd(1)),
              setting or unsetting the value  or  attributes  of  SHELL,  ENV,
              FPATH, or PATH,
              specifying path or command names containing /,
              redirecting output (>, >|, <>, and >>).
              adding or deleting built-in commands.
              using command -p to invoke a command.

       The  restrictions  above  are enforced after .profile and the ENV files
       are interpreted.

       When a command to be executed is found to be a  shell  procedure,  rksh
       invokes ksh to execute it.  Thus, it is possible to provide to the end-
       user shell procedures that have access to the full power of  the  stan-
       dard  shell,  while  imposing  a  limited menu of commands; this scheme
       assumes that the end-user does not have write and  execute  permissions
       in the same directory.

       The  net  effect  of these rules is that the writer of the .profile has
       complete control over user  actions,  by  performing  guaranteed  setup
       actions  and leaving the user in an appropriate directory (probably not
       the login directory).

       The system administrator often sets up a directory of  commands  (e.g.,
       /usr/rbin) that can be safely invoked by rksh.

EXIT STATUS
       Errors detected by the shell, such as syntax errors, cause the shell to
       return a non-zero exit status.  If the shell is being used non-interac-
       tively,  then execution of the shell file is abandoned unless the error
       occurs inside a subshell in which case the subshell is abandoned.  Oth-
       erwise,  the shell returns the exit status of the last command executed
       (see also the exit command above).  Run time  errors  detected  by  the
       shell  are  reported  by  printing the command or function name and the
       error condition.  If the line number that  the  error  occurred  on  is
       greater than one, then the line number is also printed in square brack-
       ets ([]) after the command or function name.

FILES
       /etc/profile
              The system wide initialization file, executed for login  shells.

       $HOME/.profile
              The  personal  initialization  file,  executed  for login shells
              after /etc/profile.

       $HOME/..kshrc
              Default personal initialization file, executed  for  interactive
              shells when ENV is not set.

       /etc/suid_profile
              Alternative  initialization  file,  executed instead of the per-
              sonal initialization file when the real and  effective  user  or
              group id do not match.

       /dev/null
              NULL device

SEE ALSO
       cat(1),  cd(1),  chmod(1), cut(1), egrep(1), echo(1), emacs(1), env(1),
       fgrep(1), gmacs(1), grep(1), newgrp(1),  pfexec(1),  stty(1),  test(1),
       umask(1),  vi(1),  dup(2),  exec(2),  fork(2),  getpwnam(3),  ioctl(2),
       lseek(2),  paste(1),  pathconf(2),   pipe(2),   sysconf(2),   umask(2),
       ulimit(2), wait(2), rand(3), a.out(5), profile(5), environ(7).

       Morris  I. Bolsky and David G. Korn, The New KornShell Command and Pro-
       gramming Language, Prentice Hall, 1995.

       POSIX - Part 2: Shell and  Utilities,  IEEE  Std  1003.2-1992,  ISO/IEC
       9945-2, IEEE, 1993.

CAVEATS
       If  a  command  is  executed,  and then a command with the same name is
       installed in a directory in the search path before the directory  where
       the  original  command  was  found, the shell will continue to exec the
       original command.  Use the -t option of the alias  command  to  correct
       this situation.

       Some very old shell scripts contain a ^ as a synonym for the pipe char-
       acter |.

       Using the hist built-in command within a compound  command  will  cause
       the whole command to disappear from the history file.

       The  built-in  command  . file reads the whole file before any commands
       are executed.  Therefore, alias and unalias commands in the  file  will
       not apply to any commands defined in the file.

       Traps  are  not  processed while a job is waiting for a foreground pro-
       cess.  Thus, a trap on CHLD won't be executed until the foreground  job
       terminates.

       It  is  a good idea to leave a space after the comma operator in arith-
       metic expressions to prevent the comma from being  interpreted  as  the
       decimal point character in certain locales.

RDS Standard              User Environment Utilities                    KSH(1)