Some clients can be controlled by other programs through some external communications mechanism. A WWW standard for this mechanism is still under development, but Mosaic and Netscape have their own ways of doing it.
You can direct the Mosaic Unix client to visit a particular URL by sending it messages - the Unix approach is simply to place a command in a temporary file called
where pid is the process id of the Mosaic client found by running the command to get a process status listing (e.g. ps). You then use the Unix signal facility to prompt Mosaic to take notice: kill -USR1 1234 where 1234 is the process id of Mosaic.
Commands span 2 lines and look like:
To do the same thing with netscape, you simply run another netscape and give it a command line argument. netscape -remote "openURL(http://www.cs.ucl.ac.uk/staff/jon)" This makes use of the underlying X windows system to carry the message.