Error report
type error =
The type of error codes. Errors defined in the POSIX standard and additional errors from UNIX98 and BSD. All other errors are mapped to EUNKNOWNERR.
exception Unix_error of error * string * string
Raised by the system calls below when an error is encountered. The first component is the error code; the second component is the function name; the third component is the string parameter to the function, if it has one, or the empty string otherwise.
val error_message : error -> string
Return a string describing the given error code.
val handle_unix_error : ('a -> 'b) -> 'a -> 'b
handle_unix_error f x
appliesf
tox
and returns the result. If the exceptionUnix_error
is raised, it prints a message describing the error and exits with code 2.
Access to the process environment
val environment : unit -> string array
Return the process environment, as an array of strings with the format ``variable=value''. The returned array is empty if the process has special privileges.
val unsafe_environment : unit -> string array
Return the process environment, as an array of strings with the format ``variable=value''. Unlike
environment
, this function returns a populated array even if the process has special privileges. See the documentation forunsafe_getenv
for more details.- since
- 4.06.0
val getenv : string -> string
Return the value associated to a variable in the process environment, unless the process has special privileges.
- raises Not_found
if the variable is unbound or the process has special privileges.
(This function is identical to
Sys
.getenv.
val unsafe_getenv : string -> string
Return the value associated to a variable in the process environment.
Unlike
getenv
, this function returns the value even if the process has special privileges. It is considered unsafe because the programmer of a setuid or setgid program must be careful to avoid using maliciously crafted environment variables in the search path for executables, the locations for temporary files or logs, and the like.- raises Not_found
if the variable is unbound.
- since
- 4.06.0
val putenv : string -> string -> unit
Unix.putenv name value
sets the value associated to a variable in the process environment.name
is the name of the environment variable, andvalue
its new associated value.
Process handling
type process_status =
The termination status of a process. See module
Sys
for the definitions of the standard signal numbers. Note that they are not the numbers used by the OS.
type wait_flag =
| WNOHANG
Do not block if no child has died yet, but immediately return with a pid equal to 0.
| WUNTRACED
Report also the children that receive stop signals.
Flags for
Unix.waitpid
.
val execv : string -> string array -> 'a
execv prog args
execute the program in fileprog
, with the argumentsargs
, and the current process environment. Theseexecv*
functions never return: on success, the current program is replaced by the new one.- raises Unix.Unix_error
on failure.
val execve : string -> string array -> string array -> 'a
Same as
Unix.execv
, except that the third argument provides the environment to the program executed.
val execvp : string -> string array -> 'a
Same as
Unix.execv
, except that the program is searched in the path.
val execvpe : string -> string array -> string array -> 'a
Same as
Unix.execve
, except that the program is searched in the path.
val fork : unit -> int
Fork a new process. The returned integer is 0 for the child process, the pid of the child process for the parent process.
On Windows: not implemented, use
create_process
or threads.
val wait : unit -> int * process_status
Wait until one of the children processes die, and return its pid and termination status.
On Windows: Not implemented, use
waitpid
.
val waitpid : wait_flag list -> int -> int * process_status
Same as
Unix.wait
, but waits for the child process whose pid is given. A pid of-1
means wait for any child. A pid of0
means wait for any child in the same process group as the current process. Negative pid arguments represent process groups. The list of options indicates whetherwaitpid
should return immediately without waiting, and whether it should report stopped children.On Windows, this function can only wait for a given PID, not any child process.
val system : string -> process_status
Execute the given command, wait until it terminates, and return its termination status. The string is interpreted by the shell
/bin/sh
(or the command interpretercmd.exe
on Windows) and therefore can contain redirections, quotes, variables, etc. The resultWEXITED 127
indicates that the shell couldn't be executed.
val getppid : unit -> int
Return the pid of the parent process. On Windows: not implemented (because it is meaningless).
val nice : int -> int
Change the process priority. The integer argument is added to the ``nice'' value. (Higher values of the ``nice'' value mean lower priorities.) Return the new nice value.
On Windows: not implemented.
Basic file input/output
val stdin : file_descr
File descriptor for standard input.
val stdout : file_descr
File descriptor for standard output.
val stderr : file_descr
File descriptor for standard error.
type open_flag =
| O_RDONLY
Open for reading
| O_WRONLY
Open for writing
| O_RDWR
Open for reading and writing
| O_NONBLOCK
Open in non-blocking mode
| O_APPEND
Open for append
| O_CREAT
Create if nonexistent
| O_TRUNC
Truncate to 0 length if existing
| O_EXCL
Fail if existing
| O_NOCTTY
Don't make this dev a controlling tty
| O_DSYNC
Writes complete as `Synchronised I/O data integrity completion'
| O_SYNC
Writes complete as `Synchronised I/O file integrity completion'
| O_RSYNC
Reads complete as writes (depending on O_SYNC/O_DSYNC)
| O_SHARE_DELETE
Windows only: allow the file to be deleted while still open
| O_CLOEXEC
Set the close-on-exec flag on the descriptor returned by
openfile
. Seeset_close_on_exec
for more information.| O_KEEPEXEC
Clear the close-on-exec flag. This is currently the default.
The flags to
Unix.openfile
.
type file_perm = int
The type of file access rights, e.g.
0o640
is read and write for user, read for group, none for others
val openfile : string -> open_flag list -> file_perm -> file_descr
Open the named file with the given flags. Third argument is the permissions to give to the file if it is created (see
umask
). Return a file descriptor on the named file.
val close : file_descr -> unit
Close a file descriptor.
val fsync : file_descr -> unit
Flush file buffers to disk.
val read : file_descr -> bytes -> int -> int -> int
read fd buff ofs len
readslen
bytes from descriptorfd
, storing them in byte sequencebuff
, starting at positionofs
inbuff
. Return the number of bytes actually read.
val write : file_descr -> bytes -> int -> int -> int
write fd buff ofs len
writeslen
bytes to descriptorfd
, taking them from byte sequencebuff
, starting at positionofs
inbuff
. Return the number of bytes actually written.write
repeats the writing operation until all bytes have been written or an error occurs.
val single_write : file_descr -> bytes -> int -> int -> int
Same as
write
, but attempts to write only once. Thus, if an error occurs,single_write
guarantees that no data has been written.
val write_substring : file_descr -> string -> int -> int -> int
Same as
write
, but take the data from a string instead of a byte sequence.- since
- 4.02.0
val single_write_substring : file_descr -> string -> int -> int -> int
Same as
single_write
, but take the data from a string instead of a byte sequence.- since
- 4.02.0
Interfacing with the standard input/output library
val in_channel_of_descr : file_descr -> Stdlib.in_channel
Create an input channel reading from the given descriptor. The channel is initially in binary mode; use
set_binary_mode_in ic false
if text mode is desired. Text mode is supported only if the descriptor refers to a file or pipe, but is not supported if it refers to a socket. On Windows,set_binary_mode_in
always fails on channels created with this function.Beware that channels are buffered so more characters may have been read from the file descriptor than those accessed using channel functions. Channels also keep a copy of the current position in the file.
You need to explicitly close all channels created with this function. Closing the channel also closes the underlying file descriptor (unless it was already closed).
val out_channel_of_descr : file_descr -> Stdlib.out_channel
Create an output channel writing on the given descriptor. The channel is initially in binary mode; use
set_binary_mode_out oc false
if text mode is desired. Text mode is supported only if the descriptor refers to a file or pipe, but is not supported if it refers to a socket. On Windows,set_binary_mode_out
always fails on channels created with this function.Beware that channels are buffered so you may have to
flush
them to ensure that all data has been sent to the file descriptor. Channels also keep a copy of the current position in the file.You need to explicitly close all channels created with this function. Closing the channel flushes the data and closes the underlying file descriptor (unless it has already been closed, in which case the buffered data is lost).
val descr_of_in_channel : Stdlib.in_channel -> file_descr
Return the descriptor corresponding to an input channel.
val descr_of_out_channel : Stdlib.out_channel -> file_descr
Return the descriptor corresponding to an output channel.
Seeking and truncating
type seek_command =
| SEEK_SET
indicates positions relative to the beginning of the file
| SEEK_CUR
indicates positions relative to the current position
| SEEK_END
indicates positions relative to the end of the file
Positioning modes for
Unix.lseek
.
val lseek : file_descr -> int -> seek_command -> int
Set the current position for a file descriptor, and return the resulting offset (from the beginning of the file).
val truncate : string -> int -> unit
Truncates the named file to the given size.
On Windows: not implemented.
val ftruncate : file_descr -> int -> unit
Truncates the file corresponding to the given descriptor to the given size.
On Windows: not implemented.
File status
type file_kind =
| S_REG
Regular file
| S_DIR
Directory
| S_CHR
Character device
| S_BLK
Block device
| S_LNK
Symbolic link
| S_FIFO
Named pipe
| S_SOCK
Socket
type stats = {
st_dev : int;
Device number
st_ino : int;
Inode number
st_kind : file_kind;
Kind of the file
st_perm : file_perm;
Access rights
st_nlink : int;
Number of links
st_uid : int;
User id of the owner
st_gid : int;
Group ID of the file's group
st_rdev : int;
Device ID (if special file)
st_size : int;
Size in bytes
st_atime : float;
Last access time
st_mtime : float;
Last modification time
st_ctime : float;
Last status change time
}
The information returned by the
Unix.stat
calls.
val stat : string -> stats
Return the information for the named file.
val lstat : string -> stats
Same as
Unix.stat
, but in case the file is a symbolic link, return the information for the link itself.
val fstat : file_descr -> stats
Return the information for the file associated with the given descriptor.
val isatty : file_descr -> bool
Return
true
if the given file descriptor refers to a terminal or console window,false
otherwise.
File operations on large files
module LargeFile : sig ... end
File operations on large files. This sub-module provides 64-bit variants of the functions
Unix.lseek
(for positioning a file descriptor),Unix.truncate
andUnix.ftruncate
(for changing the size of a file), andUnix.stat
,Unix.lstat
andUnix.fstat
(for obtaining information on files). These alternate functions represent positions and sizes by 64-bit integers (typeint64
) instead of regular integers (typeint
), thus allowing operating on files whose sizes are greater thanmax_int
.
Mapping files into memory
val map_file : file_descr -> ?pos:int64 -> ('a, 'b) Bigarray.kind -> 'c Bigarray.layout -> bool -> int array -> ('a, 'b, 'c) Bigarray.Genarray.t
Memory mapping of a file as a Bigarray.
map_file fd kind layout shared dims
returns a Bigarray of kindkind
, layoutlayout
, and dimensions as specified indims
. The data contained in this Bigarray are the contents of the file referred to by the file descriptorfd
(as opened previously withUnix.openfile
, for example). The optionalpos
parameter is the byte offset in the file of the data being mapped; it defaults to 0 (map from the beginning of the file).If
shared
istrue
, all modifications performed on the array are reflected in the file. This requires thatfd
be opened with write permissions. Ifshared
isfalse
, modifications performed on the array are done in memory only, using copy-on-write of the modified pages; the underlying file is not affected.Genarray.map_file
is much more efficient than reading the whole file in a Bigarray, modifying that Bigarray, and writing it afterwards.To adjust automatically the dimensions of the Bigarray to the actual size of the file, the major dimension (that is, the first dimension for an array with C layout, and the last dimension for an array with Fortran layout) can be given as
-1
.Genarray.map_file
then determines the major dimension from the size of the file. The file must contain an integral number of sub-arrays as determined by the non-major dimensions, otherwiseFailure
is raised.If all dimensions of the Bigarray are given, the file size is matched against the size of the Bigarray. If the file is larger than the Bigarray, only the initial portion of the file is mapped to the Bigarray. If the file is smaller than the big array, the file is automatically grown to the size of the Bigarray. This requires write permissions on
fd
.Array accesses are bounds-checked, but the bounds are determined by the initial call to
map_file
. Therefore, you should make sure no other process modifies the mapped file while you're accessing it, or a SIGBUS signal may be raised. This happens, for instance, if the file is shrunk.Invalid_argument
orFailure
may be raised in cases where argument validation fails.- since
- 4.06.0
Operations on file names
val unlink : string -> unit
Removes the named file.
If the named file is a directory, raises:
EPERM
on POSIX compliant systemEISDIR
on Linux >= 2.1.132EACCESS
on Windows
val rename : string -> string -> unit
rename old new
changes the name of a file fromold
tonew
, moving it between directories if needed. Ifnew
already exists, its contents will be replaced with those ofold
. Depending on the operating system, the metadata (permissions, owner, etc) ofnew
can either be preserved or be replaced by those ofold
.
val link : ?follow:bool -> string -> string -> unit
link ?follow source dest
creates a hard link nameddest
to the file namedsource
.- parameter follow
indicates whether a
source
symlink is followed or a hardlink tosource
itself will be created. On Unix systems this is done using thelinkat(2)
function. If?follow
is not provided, then thelink(2)
function is used whose behaviour is OS-dependent, but more widely available.
- raises ENOSYS
On Unix if
~follow:_
is requested, but linkat is unavailable.
- raises ENOSYS
On Windows if
~follow:false
is requested.
File permissions and ownership
type access_permission =
| R_OK
Read permission
| W_OK
Write permission
| X_OK
Execution permission
| F_OK
File exists
Flags for the
Unix.access
call.
val chmod : string -> file_perm -> unit
Change the permissions of the named file.
val fchmod : file_descr -> file_perm -> unit
Change the permissions of an opened file. On Windows: not implemented.
val chown : string -> int -> int -> unit
Change the owner uid and owner gid of the named file. On Windows: not implemented (make no sense on a DOS file system).
val fchown : file_descr -> int -> int -> unit
Change the owner uid and owner gid of an opened file. On Windows: not implemented (make no sense on a DOS file system).
val umask : int -> int
Set the process's file mode creation mask, and return the previous mask. On Windows: not implemented.
val access : string -> access_permission list -> unit
Check that the process has the given permissions over the named file.
- raises Unix_error
otherwise.
On Windows, execute permission
X_OK
, cannot be tested, it just tests for read permission instead.
Operations on file descriptors
val dup : ?cloexec:bool -> file_descr -> file_descr
Return a new file descriptor referencing the same file as the given descriptor. See
set_close_on_exec
for documentation on thecloexec
optional argument.
val dup2 : ?cloexec:bool -> file_descr -> file_descr -> unit
dup2 fd1 fd2
duplicatesfd1
tofd2
, closingfd2
if already opened. Seeset_close_on_exec
for documentation on thecloexec
optional argument.
val set_nonblock : file_descr -> unit
Set the ``non-blocking'' flag on the given descriptor. When the non-blocking flag is set, reading on a descriptor on which there is temporarily no data available raises the
EAGAIN
orEWOULDBLOCK
error instead of blocking; writing on a descriptor on which there is temporarily no room for writing also raisesEAGAIN
orEWOULDBLOCK
.
val clear_nonblock : file_descr -> unit
Clear the ``non-blocking'' flag on the given descriptor. See
Unix.set_nonblock
.
val set_close_on_exec : file_descr -> unit
Set the ``close-on-exec'' flag on the given descriptor. A descriptor with the close-on-exec flag is automatically closed when the current process starts another program with one of the
exec
,create_process
andopen_process
functions.It is often a security hole to leak file descriptors opened on, say, a private file to an external program: the program, then, gets access to the private file and can do bad things with it. Hence, it is highly recommended to set all file descriptors ``close-on-exec'', except in the very few cases where a file descriptor actually needs to be transmitted to another program.
The best way to set a file descriptor ``close-on-exec'' is to create it in this state. To this end, the
openfile
function hasO_CLOEXEC
andO_KEEPEXEC
flags to enforce ``close-on-exec'' mode or ``keep-on-exec'' mode, respectively. All other operations in the Unix module that create file descriptors have an optional argument?cloexec:bool
to indicate whether the file descriptor should be created in ``close-on-exec'' mode (by writing~cloexec:true
) or in ``keep-on-exec'' mode (by writing~cloexec:false
). For historical reasons, the default file descriptor creation mode is ``keep-on-exec'', if nocloexec
optional argument is given. This is not a safe default, hence it is highly recommended to pass explicitcloexec
arguments to operations that create file descriptors.The
cloexec
optional arguments and theO_KEEPEXEC
flag were introduced in OCaml 4.05. Earlier, the common practice was to create file descriptors in the default, ``keep-on-exec'' mode, then callset_close_on_exec
on those freshly-created file descriptors. This is not as safe as creating the file descriptor in ``close-on-exec'' mode because, in multithreaded programs, a window of vulnerability exists between the time when the file descriptor is created and the timeset_close_on_exec
completes. If another thread spawns another program during this window, the descriptor will leak, as it is still in the ``keep-on-exec'' mode.Regarding the atomicity guarantees given by
~cloexec:true
or by the use of theO_CLOEXEC
flag: on all platforms it is guaranteed that a concurrently-executing Caml thread cannot leak the descriptor by starting a new process. On Linux, this guarantee extends to concurrently-executing C threads. As of Feb 2017, other operating systems lack the necessary system calls and still expose a window of vulnerability during which a C thread can see the newly-created file descriptor in ``keep-on-exec'' mode.
val clear_close_on_exec : file_descr -> unit
Clear the ``close-on-exec'' flag on the given descriptor. See
Unix.set_close_on_exec
.
Directories
val opendir : string -> dir_handle
Open a descriptor on a directory
val readdir : dir_handle -> string
Return the next entry in a directory.
- raises End_of_file
when the end of the directory has been reached.
val rewinddir : dir_handle -> unit
Reposition the descriptor to the beginning of the directory
val closedir : dir_handle -> unit
Close a directory descriptor.
Pipes and redirections
val pipe : ?cloexec:bool -> unit -> file_descr * file_descr
Create a pipe. The first component of the result is opened for reading, that's the exit to the pipe. The second component is opened for writing, that's the entrance to the pipe. See
set_close_on_exec
for documentation on thecloexec
optional argument.
val mkfifo : string -> file_perm -> unit
Create a named pipe with the given permissions (see
umask
). On Windows: not implemented.
High-level process and redirection management
val create_process : string -> string array -> file_descr -> file_descr -> file_descr -> int
create_process prog args new_stdin new_stdout new_stderr
forks a new process that executes the program in fileprog
, with argumentsargs
. The pid of the new process is returned immediately; the new process executes concurrently with the current process. The standard input and outputs of the new process are connected to the descriptorsnew_stdin
,new_stdout
andnew_stderr
. Passing e.g.stdout
fornew_stdout
prevents the redirection and causes the new process to have the same standard output as the current process. The executable fileprog
is searched in the path. The new process has the same environment as the current process.
val create_process_env : string -> string array -> string array -> file_descr -> file_descr -> file_descr -> int
create_process_env prog args env new_stdin new_stdout new_stderr
works asUnix.create_process
, except that the extra argumentenv
specifies the environment passed to the program.
val open_process_in : string -> Stdlib.in_channel
High-level pipe and process management. This function runs the given command in parallel with the program. The standard output of the command is redirected to a pipe, which can be read via the returned input channel. The command is interpreted by the shell
/bin/sh
(orcmd.exe
on Windows), cf.system
.
val open_process_out : string -> Stdlib.out_channel
Same as
Unix.open_process_in
, but redirect the standard input of the command to a pipe. Data written to the returned output channel is sent to the standard input of the command. Warning: writes on output channels are buffered, hence be careful to callStdlib.flush
at the right times to ensure correct synchronization.
val open_process : string -> Stdlib.in_channel * Stdlib.out_channel
Same as
Unix.open_process_out
, but redirects both the standard input and standard output of the command to pipes connected to the two returned channels. The input channel is connected to the output of the command, and the output channel to the input of the command.
val open_process_full : string -> string array -> Stdlib.in_channel * Stdlib.out_channel * Stdlib.in_channel
Similar to
Unix.open_process
, but the second argument specifies the environment passed to the command. The result is a triple of channels connected respectively to the standard output, standard input, and standard error of the command.
val open_process_args_in : string -> string array -> Stdlib.in_channel
High-level pipe and process management. The first argument specifies the command to run, and the second argument specifies the argument array passed to the command. This function runs the command in parallel with the program. The standard output of the command is redirected to a pipe, which can be read via the returned input channel.
- since
- 4.08.0
val open_process_args_out : string -> string array -> Stdlib.out_channel
Same as
Unix.open_process_args_in
, but redirect the standard input of the command to a pipe. Data written to the returned output channel is sent to the standard input of the command. Warning: writes on output channels are buffered, hence be careful to callStdlib.flush
at the right times to ensure correct synchronization.- since
- 4.08.0
val open_process_args : string -> string array -> Stdlib.in_channel * Stdlib.out_channel
Same as
Unix.open_process_args_out
, but redirects both the standard input and standard output of the command to pipes connected to the two returned channels. The input channel is connected to the output of the command, and the output channel to the input of the command.- since
- 4.08.0
val open_process_args_full : string -> string array -> string array -> Stdlib.in_channel * Stdlib.out_channel * Stdlib.in_channel
Similar to
Unix.open_process_args
, but the third argument specifies the environment passed to the command. The result is a triple of channels connected respectively to the standard output, standard input, and standard error of the command.- since
- 4.08.0
val process_in_pid : Stdlib.in_channel -> int
Return the pid of a process opened via
Unix.open_process_in
orUnix.open_process_args_in
.- since
- 4.08.0
val process_out_pid : Stdlib.out_channel -> int
Return the pid of a process opened via
Unix.open_process_out
orUnix.open_process_args_out
.- since
- 4.08.0
val process_pid : (Stdlib.in_channel * Stdlib.out_channel) -> int
Return the pid of a process opened via
Unix.open_process
orUnix.open_process_args
.- since
- 4.08.0
val process_full_pid : (Stdlib.in_channel * Stdlib.out_channel * Stdlib.in_channel) -> int
Return the pid of a process opened via
Unix.open_process_full
orUnix.open_process_args_full
.- since
- 4.08.0
val close_process_in : Stdlib.in_channel -> process_status
Close channels opened by
Unix.open_process_in
, wait for the associated command to terminate, and return its termination status.
val close_process_out : Stdlib.out_channel -> process_status
Close channels opened by
Unix.open_process_out
, wait for the associated command to terminate, and return its termination status.
val close_process : (Stdlib.in_channel * Stdlib.out_channel) -> process_status
Close channels opened by
Unix.open_process
, wait for the associated command to terminate, and return its termination status.
val close_process_full : (Stdlib.in_channel * Stdlib.out_channel * Stdlib.in_channel) -> process_status
Close channels opened by
Unix.open_process_full
, wait for the associated command to terminate, and return its termination status.
Symbolic links
val symlink : ?to_dir:bool -> string -> string -> unit
symlink ?to_dir source dest
creates the filedest
as a symbolic link to the filesource
. On Windows,~to_dir
indicates if the symbolic link points to a directory or a file; if omitted,symlink
examinessource
usingstat
and picks appropriately, ifsource
does not exist thenfalse
is assumed (for this reason, it is recommended that the~to_dir
parameter be specified in new code). On Unix,~to_dir
is ignored.Windows symbolic links are available in Windows Vista onwards. There are some important differences between Windows symlinks and their POSIX counterparts.
Windows symbolic links come in two flavours: directory and regular, which designate whether the symbolic link points to a directory or a file. The type must be correct - a directory symlink which actually points to a file cannot be selected with chdir and a file symlink which actually points to a directory cannot be read or written (note that Cygwin's emulation layer ignores this distinction).
When symbolic links are created to existing targets, this distinction doesn't matter and
symlink
will automatically create the correct kind of symbolic link. The distinction matters when a symbolic link is created to a non-existent target.The other caveat is that by default symbolic links are a privileged operation. Administrators will always need to be running elevated (or with UAC disabled) and by default normal user accounts need to be granted the SeCreateSymbolicLinkPrivilege via Local Security Policy (secpol.msc) or via Active Directory.
has_symlink
can be used to check that a process is able to create symbolic links.
val has_symlink : unit -> bool
Returns
true
if the user is able to create symbolic links. On Windows, this indicates that the user not only has the SeCreateSymbolicLinkPrivilege but is also running elevated, if necessary. On other platforms, this is simply indicates that the symlink system call is available.- since
- 4.03.0
Polling
val select : file_descr list -> file_descr list -> file_descr list -> float -> file_descr list * file_descr list * file_descr list
Wait until some input/output operations become possible on some channels. The three list arguments are, respectively, a set of descriptors to check for reading (first argument), for writing (second argument), or for exceptional conditions (third argument). The fourth argument is the maximal timeout, in seconds; a negative fourth argument means no timeout (unbounded wait). The result is composed of three sets of descriptors: those ready for reading (first component), ready for writing (second component), and over which an exceptional condition is pending (third component).
Locking
type lock_command =
Commands for
Unix.lockf
.
val lockf : file_descr -> lock_command -> int -> unit
lockf fd cmd size
puts a lock on a region of the file opened asfd
. The region starts at the current read/write position forfd
(as set byUnix.lseek
), and extendssize
bytes forward ifsize
is positive,size
bytes backwards ifsize
is negative, or to the end of the file ifsize
is zero. A write lock prevents any other process from acquiring a read or write lock on the region. A read lock prevents any other process from acquiring a write lock on the region, but lets other processes acquire read locks on it.The
F_LOCK
andF_TLOCK
commands attempts to put a write lock on the specified region. TheF_RLOCK
andF_TRLOCK
commands attempts to put a read lock on the specified region. If one or several locks put by another process prevent the current process from acquiring the lock,F_LOCK
andF_RLOCK
block until these locks are removed, whileF_TLOCK
andF_TRLOCK
fail immediately with an exception. TheF_ULOCK
removes whatever locks the current process has on the specified region. Finally, theF_TEST
command tests whether a write lock can be acquired on the specified region, without actually putting a lock. It returns immediately if successful, or fails otherwise.What happens when a process tries to lock a region of a file that is already locked by the same process depends on the OS. On POSIX-compliant systems, the second lock operation succeeds and may "promote" the older lock from read lock to write lock. On Windows, the second lock operation will block or fail.
Signals
val kill : int -> int -> unit
kill pid sig
sends signal numbersig
to the process with idpid
. On Windows, only theSys
.sigkill signal is emulated.
val sigprocmask : sigprocmask_command -> int list -> int list
sigprocmask cmd sigs
changes the set of blocked signals. Ifcmd
isSIG_SETMASK
, blocked signals are set to those in the listsigs
. Ifcmd
isSIG_BLOCK
, the signals insigs
are added to the set of blocked signals. Ifcmd
isSIG_UNBLOCK
, the signals insigs
are removed from the set of blocked signals.sigprocmask
returns the set of previously blocked signals.When the systhreads version of the
Thread
module is loaded, this function redirects toThread.sigmask
. I.e.,sigprocmask
only changes the mask of the current thread.On Windows: not implemented (no inter-process signals on Windows).
val sigpending : unit -> int list
Return the set of blocked signals that are currently pending.
On Windows: not implemented (no inter-process signals on Windows).
val sigsuspend : int list -> unit
sigsuspend sigs
atomically sets the blocked signals tosigs
and waits for a non-ignored, non-blocked signal to be delivered. On return, the blocked signals are reset to their initial value.On Windows: not implemented (no inter-process signals on Windows).
val pause : unit -> unit
Wait until a non-ignored, non-blocked signal is delivered.
On Windows: not implemented (no inter-process signals on Windows).
Time functions
type process_times = {
}
The execution times (CPU times) of a process.
type tm = {
}
The type representing wallclock time and calendar date.
val gettimeofday : unit -> float
Same as
Unix.time
, but with resolution better than 1 second.
val gmtime : float -> tm
Convert a time in seconds, as returned by
Unix.time
, into a date and a time. Assumes UTC (Coordinated Universal Time), also known as GMT. To perform the inverse conversion, set the TZ environment variable to "UTC", usemktime
, and then restore the original value of TZ.
val localtime : float -> tm
Convert a time in seconds, as returned by
Unix.time
, into a date and a time. Assumes the local time zone. The function performing the inverse conversion ismktime
.
val mktime : tm -> float * tm
Convert a date and time, specified by the
tm
argument, into a time in seconds, as returned byUnix.time
. Thetm_isdst
,tm_wday
andtm_yday
fields oftm
are ignored. Also return a normalized copy of the giventm
record, with thetm_wday
,tm_yday
, andtm_isdst
fields recomputed from the other fields, and the other fields normalized (so that, e.g., 40 October is changed into 9 November). Thetm
argument is interpreted in the local time zone.
val alarm : int -> int
Schedule a
SIGALRM
signal after the given number of seconds.On Windows: not implemented.
val sleepf : float -> unit
Stop execution for the given number of seconds. Like
sleep
, but fractions of seconds are supported.- since
- 4.03.0
val times : unit -> process_times
Return the execution times of the process. On Windows, it is partially implemented, will not report timings for child processes.
val utimes : string -> float -> float -> unit
Set the last access time (second arg) and last modification time (third arg) for a file. Times are expressed in seconds from 00:00:00 GMT, Jan. 1, 1970. If both times are
0.0
, the access and last modification times are both set to the current time.
type interval_timer =
The three kinds of interval timers.
type interval_timer_status = {
it_interval : float;
Period
it_value : float;
Current value of the timer
}
The type describing the status of an interval timer
val getitimer : interval_timer -> interval_timer_status
Return the current status of the given interval timer.
On Windows: not implemented.
val setitimer : interval_timer -> interval_timer_status -> interval_timer_status
setitimer t s
sets the interval timert
and returns its previous status. Thes
argument is interpreted as follows:s.it_value
, if nonzero, is the time to the next timer expiration;s.it_interval
, if nonzero, specifies a value to be used in reloadingit_value
when the timer expires. Settings.it_value
to zero disables the timer. Settings.it_interval
to zero causes the timer to be disabled after its next expiration.On Windows: not implemented.
User id, group id
val getuid : unit -> int
Return the user id of the user executing the process. On Windows, always return
1
.
val geteuid : unit -> int
Return the effective user id under which the process runs. On Windows, always return
1
.
val setuid : int -> unit
Set the real user id and effective user id for the process. On Windows: not implemented.
val getgid : unit -> int
Return the group id of the user executing the process. On Windows, always return
1
.
val getegid : unit -> int
Return the effective group id under which the process runs. On Windows, always return
1
.
val setgid : int -> unit
Set the real group id and effective group id for the process. On Windows: not implemented.
val getgroups : unit -> int array
Return the list of groups to which the user executing the process belongs. On Windows, always return
[|1|]
.
val setgroups : int array -> unit
setgroups groups
sets the supplementary group IDs for the calling process. Appropriate privileges are required. On Windows: not implemented.
val initgroups : string -> int -> unit
initgroups user group
initializes the group access list by reading the group database /etc/group and using all groups of whichuser
is a member. The additional groupgroup
is also added to the list. On Windows: not implemented.
type passwd_entry = {
pw_name : string;
pw_passwd : string;
pw_uid : int;
pw_gid : int;
pw_gecos : string;
pw_dir : string;
pw_shell : string;
}
Structure of entries in the
passwd
database.
type group_entry = {
gr_name : string;
gr_passwd : string;
gr_gid : int;
gr_mem : string array;
}
Structure of entries in the
groups
database.
val getpwnam : string -> passwd_entry
Find an entry in
passwd
with the given name.- raises Not_found
if no such entry exist.
On Windows, always raise
Not_found
.
val getgrnam : string -> group_entry
Find an entry in
group
with the given name.- raises Not_found
if no such entry exist.
On Windows, always raise
Not_found
.
val getpwuid : int -> passwd_entry
Find an entry in
passwd
with the given user id.- raises Not_found
if no such entry exist.
On Windows, always raise
Not_found
.
val getgrgid : int -> group_entry
Find an entry in
group
with the given group id.- raises Not_found
if no such entry exist.
On Windows, always raise
Not_found
.
Internet addresses
val inet_addr_of_string : string -> inet_addr
Conversion from the printable representation of an Internet address to its internal representation. The argument string consists of 4 numbers separated by periods (
XXX.YYY.ZZZ.TTT
) for IPv4 addresses, and up to 8 numbers separated by colons for IPv6 addresses.- raises Failure
when given a string that does not match these formats.
val string_of_inet_addr : inet_addr -> string
Return the printable representation of the given Internet address. See
Unix.inet_addr_of_string
for a description of the printable representation.
val inet_addr_any : inet_addr
A special IPv4 address, for use only with
bind
, representing all the Internet addresses that the host machine possesses.
val inet_addr_loopback : inet_addr
A special IPv4 address representing the host machine (
127.0.0.1
).
val inet6_addr_any : inet_addr
A special IPv6 address, for use only with
bind
, representing all the Internet addresses that the host machine possesses.
val inet6_addr_loopback : inet_addr
A special IPv6 address representing the host machine (
::1
).
Sockets
type socket_domain =
| PF_UNIX
Unix domain
| PF_INET
Internet domain (IPv4)
| PF_INET6
Internet domain (IPv6)
The type of socket domains. Not all platforms support IPv6 sockets (type
PF_INET6
). Windows does not supportPF_UNIX
.
type socket_type =
| SOCK_STREAM
Stream socket
| SOCK_DGRAM
Datagram socket
| SOCK_RAW
Raw socket
| SOCK_SEQPACKET
Sequenced packets socket
The type of socket kinds, specifying the semantics of communications.
SOCK_SEQPACKET
is included for completeness, but is rarely supported by the OS, and needs system calls that are not available in this library.
type sockaddr =
| ADDR_UNIX of string
| ADDR_INET of inet_addr * int
The type of socket addresses.
ADDR_UNIX name
is a socket address in the Unix domain;name
is a file name in the file system.ADDR_INET(addr,port)
is a socket address in the Internet domain;addr
is the Internet address of the machine, andport
is the port number.
val socket : ?cloexec:bool -> socket_domain -> socket_type -> int -> file_descr
Create a new socket in the given domain, and with the given kind. The third argument is the protocol type; 0 selects the default protocol for that kind of sockets. See
set_close_on_exec
for documentation on thecloexec
optional argument.
val domain_of_sockaddr : sockaddr -> socket_domain
Return the socket domain adequate for the given socket address.
val socketpair : ?cloexec:bool -> socket_domain -> socket_type -> int -> file_descr * file_descr
Create a pair of unnamed sockets, connected together. See
set_close_on_exec
for documentation on thecloexec
optional argument.
val accept : ?cloexec:bool -> file_descr -> file_descr * sockaddr
Accept connections on the given socket. The returned descriptor is a socket connected to the client; the returned address is the address of the connecting client. See
set_close_on_exec
for documentation on thecloexec
optional argument.
val bind : file_descr -> sockaddr -> unit
Bind a socket to an address.
val connect : file_descr -> sockaddr -> unit
Connect a socket to an address.
val listen : file_descr -> int -> unit
Set up a socket for receiving connection requests. The integer argument is the maximal number of pending requests.
type shutdown_command =
| SHUTDOWN_RECEIVE
Close for receiving
| SHUTDOWN_SEND
Close for sending
| SHUTDOWN_ALL
Close both
The type of commands for
shutdown
.
val shutdown : file_descr -> shutdown_command -> unit
Shutdown a socket connection.
SHUTDOWN_SEND
as second argument causes reads on the other end of the connection to return an end-of-file condition.SHUTDOWN_RECEIVE
causes writes on the other end of the connection to return a closed pipe condition (SIGPIPE
signal).
val getsockname : file_descr -> sockaddr
Return the address of the given socket.
val getpeername : file_descr -> sockaddr
Return the address of the host connected to the given socket.
type msg_flag =
| MSG_OOB
| MSG_DONTROUTE
| MSG_PEEK
The flags for
Unix.recv
,Unix.recvfrom
,Unix.send
andUnix.sendto
.
val recv : file_descr -> bytes -> int -> int -> msg_flag list -> int
Receive data from a connected socket.
val recvfrom : file_descr -> bytes -> int -> int -> msg_flag list -> int * sockaddr
Receive data from an unconnected socket.
val send : file_descr -> bytes -> int -> int -> msg_flag list -> int
Send data over a connected socket.
val send_substring : file_descr -> string -> int -> int -> msg_flag list -> int
Same as
send
, but take the data from a string instead of a byte sequence.- since
- 4.02.0
val sendto : file_descr -> bytes -> int -> int -> msg_flag list -> sockaddr -> int
Send data over an unconnected socket.
val sendto_substring : file_descr -> string -> int -> int -> msg_flag list -> sockaddr -> int
Same as
sendto
, but take the data from a string instead of a byte sequence.- since
- 4.02.0
Socket options
type socket_bool_option =
The socket options that can be consulted with
Unix.getsockopt
and modified withUnix.setsockopt
. These options have a boolean (true
/false
) value.
type socket_int_option =
| SO_SNDBUF
Size of send buffer
| SO_RCVBUF
Size of received buffer
| SO_ERROR
Deprecated. Use
Unix.getsockopt_error
instead.| SO_TYPE
Report the socket type
| SO_RCVLOWAT
Minimum number of bytes to process for input operations
| SO_SNDLOWAT
Minimum number of bytes to process for output operations
The socket options that can be consulted with
Unix.getsockopt_int
and modified withUnix.setsockopt_int
. These options have an integer value.
type socket_optint_option =
| SO_LINGER
Whether to linger on closed connections that have data present, and for how long (in seconds)
The socket options that can be consulted with
Unix.getsockopt_optint
and modified withUnix.setsockopt_optint
. These options have a value of typeint option
, withNone
meaning ``disabled''.
type socket_float_option =
| SO_RCVTIMEO
Timeout for input operations
| SO_SNDTIMEO
Timeout for output operations
The socket options that can be consulted with
Unix.getsockopt_float
and modified withUnix.setsockopt_float
. These options have a floating-point value representing a time in seconds. The value 0 means infinite timeout.
val getsockopt : file_descr -> socket_bool_option -> bool
Return the current status of a boolean-valued option in the given socket.
val setsockopt : file_descr -> socket_bool_option -> bool -> unit
Set or clear a boolean-valued option in the given socket.
val getsockopt_int : file_descr -> socket_int_option -> int
Same as
Unix.getsockopt
for an integer-valued socket option.
val setsockopt_int : file_descr -> socket_int_option -> int -> unit
Same as
Unix.setsockopt
for an integer-valued socket option.
val getsockopt_optint : file_descr -> socket_optint_option -> int option
Same as
Unix.getsockopt
for a socket option whose value is anint option
.
val setsockopt_optint : file_descr -> socket_optint_option -> int option -> unit
Same as
Unix.setsockopt
for a socket option whose value is anint option
.
val getsockopt_float : file_descr -> socket_float_option -> float
Same as
Unix.getsockopt
for a socket option whose value is a floating-point number.
val setsockopt_float : file_descr -> socket_float_option -> float -> unit
Same as
Unix.setsockopt
for a socket option whose value is a floating-point number.
val getsockopt_error : file_descr -> error option
Return the error condition associated with the given socket, and clear it.
High-level network connection functions
val open_connection : sockaddr -> Stdlib.in_channel * Stdlib.out_channel
Connect to a server at the given address. Return a pair of buffered channels connected to the server. Remember to call
Stdlib.flush
on the output channel at the right times to ensure correct synchronization.
val shutdown_connection : Stdlib.in_channel -> unit
``Shut down'' a connection established with
Unix.open_connection
; that is, transmit an end-of-file condition to the server reading on the other side of the connection. This does not fully close the file descriptor associated with the channel, which you must remember to free viaStdlib.close_in
.
val establish_server : (Stdlib.in_channel -> Stdlib.out_channel -> unit) -> sockaddr -> unit
Establish a server on the given address. The function given as first argument is called for each connection with two buffered channels connected to the client. A new process is created for each connection. The function
Unix.establish_server
never returns normally.On Windows, it is not implemented. Use threads.
Host and protocol databases
type host_entry = {
h_name : string;
h_aliases : string array;
h_addrtype : socket_domain;
h_addr_list : inet_addr array;
}
Structure of entries in the
hosts
database.
type protocol_entry = {
p_name : string;
p_aliases : string array;
p_proto : int;
}
Structure of entries in the
protocols
database.
type service_entry = {
s_name : string;
s_aliases : string array;
s_port : int;
s_proto : string;
}
Structure of entries in the
services
database.
val gethostbyname : string -> host_entry
Find an entry in
hosts
with the given name.- raises Not_found
if no such entry exist.
val gethostbyaddr : inet_addr -> host_entry
Find an entry in
hosts
with the given address.- raises Not_found
if no such entry exist.
val getprotobyname : string -> protocol_entry
Find an entry in
protocols
with the given name.- raises Not_found
if no such entry exist.
val getprotobynumber : int -> protocol_entry
Find an entry in
protocols
with the given protocol number.- raises Not_found
if no such entry exist.
val getservbyname : string -> string -> service_entry
Find an entry in
services
with the given name.- raises Not_found
if no such entry exist.
val getservbyport : int -> string -> service_entry
Find an entry in
services
with the given service number.- raises Not_found
if no such entry exist.
type addr_info = {
ai_family : socket_domain;
Socket domain
ai_socktype : socket_type;
Socket type
ai_protocol : int;
Socket protocol number
ai_addr : sockaddr;
Address
ai_canonname : string;
Canonical host name
}
Address information returned by
Unix.getaddrinfo
.
type getaddrinfo_option =
| AI_FAMILY of socket_domain
Impose the given socket domain
| AI_SOCKTYPE of socket_type
Impose the given socket type
| AI_PROTOCOL of int
Impose the given protocol
| AI_NUMERICHOST
Do not call name resolver, expect numeric IP address
| AI_CANONNAME
Fill the
ai_canonname
field of the result| AI_PASSIVE
Set address to ``any'' address for use with
Unix.bind
Options to
Unix.getaddrinfo
.
val getaddrinfo : string -> string -> getaddrinfo_option list -> addr_info list
getaddrinfo host service opts
returns a list ofUnix.addr_info
records describing socket parameters and addresses suitable for communicating with the given host and service. The empty list is returned if the host or service names are unknown, or the constraints expressed inopts
cannot be satisfied.host
is either a host name or the string representation of an IP address.host
can be given as the empty string; in this case, the ``any'' address or the ``loopback'' address are used, depending whetheropts
containsAI_PASSIVE
.service
is either a service name or the string representation of a port number.service
can be given as the empty string; in this case, the port field of the returned addresses is set to 0.opts
is a possibly empty list of options that allows the caller to force a particular socket domain (e.g. IPv6 only or IPv4 only) or a particular socket type (e.g. TCP only or UDP only).
type name_info = {
ni_hostname : string;
Name or IP address of host
ni_service : string;
Name of service or port number
}
Host and service information returned by
Unix.getnameinfo
.
type getnameinfo_option =
Options to
Unix.getnameinfo
.
val getnameinfo : sockaddr -> getnameinfo_option list -> name_info
getnameinfo addr opts
returns the host name and service name corresponding to the socket addressaddr
.opts
is a possibly empty list of options that governs how these names are obtained.- raises Not_found
if an error occurs.
Terminal interface
type terminal_io = {
}
val tcgetattr : file_descr -> terminal_io
Return the status of the terminal referred to by the given file descriptor. On Windows, not implemented.
val tcsetattr : file_descr -> setattr_when -> terminal_io -> unit
Set the status of the terminal referred to by the given file descriptor. The second argument indicates when the status change takes place: immediately (
TCSANOW
), when all pending output has been transmitted (TCSADRAIN
), or after flushing all input that has been received but not read (TCSAFLUSH
).TCSADRAIN
is recommended when changing the output parameters;TCSAFLUSH
, when changing the input parameters.On Windows, not implemented.
val tcsendbreak : file_descr -> int -> unit
Send a break condition on the given file descriptor. The second argument is the duration of the break, in 0.1s units; 0 means standard duration (0.25s).
On Windows, not implemented.
val tcdrain : file_descr -> unit
Waits until all output written on the given file descriptor has been transmitted.
On Windows, not implemented.
val tcflush : file_descr -> flush_queue -> unit
Discard data written on the given file descriptor but not yet transmitted, or data received but not yet read, depending on the second argument:
TCIFLUSH
flushes data received but not read,TCOFLUSH
flushes data written but not transmitted, andTCIOFLUSH
flushes both.On Windows, not implemented.
val tcflow : file_descr -> flow_action -> unit
Suspend or restart reception or transmission of data on the given file descriptor, depending on the second argument:
TCOOFF
suspends output,TCOON
restarts output,TCIOFF
transmits a STOP character to suspend input, andTCION
transmits a START character to restart input.On Windows, not implemented.