Is it possible to catch a key combination like ctrl-c from within a shell script ? if it is possible,
please advise me how to do it !

Here is a more detailed picture of my problem:

A shell script is launching an app with certain parameters (i.e start table, and how many tables to process (step)). If i press ctrl-c, The app "knows how" to handle the ctrl-c, and saves it's temporary work where it should. but the script will launch the app with the next set of parameters (i have a while loop, which exits when it reaches the 256th table):

#!/bin/sh

nr_threads=20
start_table=0
step=16
export out=0

while [ $start_table -lt 256 ]
do
launch="./index -t:$nr_threads -b:$start_table -s:$step"
echo "$launch"
$launch
let "start_table = $start_table + $step"
done

what i want exactly, is to terminate the script itself, after a ctrl-c was pressed.

You can catch signals with the trap command :

trap "echo CTRL-C was pressed" 2 ( 2 is the SIGINT signal, generated by pressing CTRL-C )

ok, thanks ;-). this is the type of answer, that makes me smile ;-)

Yes you can use the trap command. The general syntax of the command is :
The command command is executed when the signal signal is caught
Since scripts are normally interpreted from top to bottom, so you must specify the trap command before the part of the script you wish to protect.
The signal INT (value = 2) is generally passed when you press CTRL-C. Type man signal to know more about signals.


You're saying that when you press CTRL-C the application knows what to do, i.e. it gets the signal and quits whereas the script doesn't quit and launches the application again and again with another set of parameter until the while loop is over. Right?

You want that the script should terminate whenever a CTRl-C signal is passed.


This is wierd at least to me. I tried calling another script form one script and then pressing CTRL-C, both scripts terminated for me. I don't know why only the application is terminating in your case and not the script also.


You could try something like this :
If you solved the problem do let us know. Many other people might be having similar problems.
Hope this helps!

well, first thanks for such a thorough reply ;-) ! The answer if I succedeed to solve this problem is yes ;-). Here is how: when an app terminates it normally should return a 0. All I did, was to return from my application a non-zero value, which I "caught" it from the script ($? is the return code). Like this if I press CtrlC, my app finishes nicely what it was doing (i.e to process current record, not the remaining of the table), and returns 1. Now when the app exits , the next if, is going to terminate the script ;-).

#!/bin/sh

nr_threads=10
start_table=0
step=16

while [ $start_table -lt 256 ]

do
launch="./index -t:$nr_threads -b:$start_table -s:$step"
$launch
if [ $? -ne 0 ]
then
exit 1
fi
let "start_table = $start_table + $step"
done