BASH how to execute a command on script termination?

Question

I have a bash script which serves as a driver basically. For some reason Ubuntu cannot assign the Bluetooth Serial port on it's own. The script's function is to connect up a bluetooth device, then assign it a place to be accessed in /dev/bluetooth serial. Finally, when the device is disconnected, or terminated by pressing "q", it kills the port.

I would like to know if there is some way to execute a command in a bash script when the ctrl-C is executed so that it does not leave the unusable device in place in my /dev folder

Callie J · Accepted Answer · 2010-11-07 14:42:23Z

17

Yep, you can use the 'trap' command. Hitting CTRL-C sends a SIGINT, so we can use trap to catch that:

#!/bin/bash

trap "echo hello world" INT

sleep 10

If you hit CTRL-C when this runs, it'll execute the command (echo hello world) :-)

answered Nov 7, 2010 at 14:42

Callie J

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1 Comment

QkiZ Over a year ago

Can be used in loop? For example: do something until Ctrl+c is pressed.

Logan Capaldo · Accepted Answer · 2010-11-07 14:39:21Z

 $ help trap

 trap: trap [-lp] [arg signal_spec ...]
     The command ARG is to be read and executed when the shell receives
     signal(s) SIGNAL_SPEC.  If ARG is absent (and a single SIGNAL_SPEC
     is supplied) or `-', each specified signal is reset to its original
     value.  If ARG is the null string each SIGNAL_SPEC is ignored by the
     shell and by the commands it invokes.  If a SIGNAL_SPEC is EXIT (0)
     the command ARG is executed on exit from the shell.  If a SIGNAL_SPEC
     is DEBUG, ARG is executed after every simple command.  If the`-p' option
     is supplied then the trap commands associated with each SIGNAL_SPEC are
     displayed.  If no arguments are supplied or if only `-p' is given, trap
     prints the list of commands associated with each signal.  Each SIGNAL_SPEC
     is either a signal name in <signal.h> or a signal number.  Signal names
     are case insensitive and the SIG prefix is optional.  `trap -l' prints
     a list of signal names and their corresponding numbers.  Note that a
     signal can be sent to the shell with "kill -signal $$".

Dennis Williamson · Accepted Answer · 2010-11-07 14:40:10Z

0

Use a trap.

trap "do_something" SIGINT

where "do_something" is a command or function name.

answered Nov 7, 2010 at 14:40

Dennis Williamson

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