Writing Deskshell commands

Standard signals

A number of standard signals are defined in the system thread, and these can be used in other threads for particular functions. The default signal is sigint, and this is used if no signal name is given in the kill command. By default, this displays a for_info dialog box and then terminates the thread with an exit command.

Threads that need to exit in a particular way can redefine sigint. The example in ``Signals'' could also have been written to use sigint rather than the user defined signal sigstop.

The sigexit signal is sent to the thread when it terminates. Normally no sigexit function is defined, so this has no action and the thread terminates immediately. However, you can define a sigexit function if you need to perform some cleaning up when the thread exits, such as deleting temporary files.

The signal sigkill causes a thread to terminate immediately, without calling the sigexit or sigkill functions.