controlling ^C and ^D characters in shell script

use:
   "trap" statement to do the job.

   eg:
   (For ksh script:
    trap "command" 0 1 2 15
    where: 0 -- shell exit, 1-- hangup
           2-- interupt     3--quit
           15 terminate

    the "command" is the job you want to do before terminated the script.

    eg. you can define a function in a ksh script, like the
followings:

    cleanup ()
{
      ec=$1

  case "$ec"
  in
     "$USAGE_EC")  Log "Usage:\t$PROG DeviceName" ;;
     "$NOMNT_EC")  Log "Error:\t$PROG: Invalid device name" ;;
     "$NOTAP_EC")  Log "Error:\t$PROG: ${DEVICE} is not available or no tape" ;;
     "$LISTE_EC")  Log "Error:\t$PROG: failed to create home list for tarring";;
     "$NOTAR_EC")  Log "Error:\t$PROG: tar command failed." ;;
     "$NOLOG_EC")  Log "Error:\t$PROG: could not initialise log file." ;;
     "$TRAPP_EC")  Log "Error:\t$PROG: abnormal program termination" ;;
     *) ;;
  esac

  mt -f $DEVICE rewind >/dev/null 2>&1
    mail ${SUPERVISOR} < $LOGFILE

  trap '' 0 1 2 15

  exit "$ec"
}                                                                                                                       AND put the following statement in the beginning of your script, after your var declearations.    
                             
# Trap on exit/interrupt/break to clean up
#
  trap "cleanup $TRAPP_EC"  0 1 2 15

  The syntax for sh is similar to ksh, as you can define function with ksh script, I perfer to use ksh


                                                   


 

The above example is from one of my backup script. the cleanup function, send me an email about the backup status before it is terminated.

yuzh,

can you give me trap script for my example...
in bash...

Here's the example for you:

#!/usr/bin/bash
# function
mytrap()
{
echo "Enter your id"
read id
echo $id
trap '' 0 1 2 15

}
# mail
trap "mytrap"  0 1 2 15


echo "this is a testscript"  
#===============================
# please use which bash to frind out where is your bash
# and modify the first line of this script

cheers!
==========
yuzh                                            

Sorry I make a typing mistake.
#"mail" suppose to be "Main", your script main body, in this case, it just do a function call"

The Main body should look like:


#main
trap "mytrap"  0 1 2 15

echo "this is a testscript"  
mytrap
# End

Hi Yuzh,
THanks this is working for ^C only....what about ^D  ..?
if i press ^D it is coming out of script.



msnr

Hi yuzh,

I will accept your answer as solution, but  ^D is working for only once....if i press second time ^D it is coming out of script..do u know why.?


msnr

Unfortunately Ctrl D is system signal for end of input from the top level of the shell, the first time you press ^D it calls the funtion mytrap(), and the second time you press it again, it exit from the the function and terminated the script. (^D is mapped signal 0 or EXIT)

If you only need to trap ^D, there is a way to get around the problem:

you put the following statement in the beginning of the script:
stty intr "^D"
# intr was map to ^C by default, if you use the above statement, you'll not be able to trap ^C

put the following statement inside the function:
stty intr "^C"
#make the intrrupt sigal back to the system default

I believe that this get arroud is not a REAL solution.