Learning Linux Shell Scripting - Second Edition

Using the trap command

If a signal or software interrupt is generated while the script is running, then we can define what action is performed by that interrupt handler using the trap command. The trap command helps us in re-assigning the system response to a particular signal through the user-defined function or commands.

The syntax to use the trap command is either of the following:

    $ trap 'command; command' signal-name
    $ trap 'command; command' signal-number

The usage as per the preceding syntax is as follows:

    trap 'echo "You pressed Control key" '  0 1 2 15

This will print the message You pressed Control key, when any of the signals SIGINT, SIGHUP, or SIGTERM are received by the process:

    trap 'rm file.tmp; echo "file.tmp is deleted" ...