ctrl+c – Ryan Schulze

Bash snippet, verify ctrl+c

July 10, 2013August 27, 2013Ryanbash, ctrl+c, trap

Lately I’ve been working on a pair of more elaborate scripts using ncat and openssl to transfer data between hosts. I’ll get around to posting it eventually, but until then a few small snippets that people may find useful.

Today we will catch ctrl+c and ask the user if he really want’s to terminate the script.

#!/bin/bash

initialize() { #{{{
  # Treat unset variables as an error
  set -o nounset
  trap verify_quit INT # verify ending script
  trap cleanup TERM EXIT # clean up if script exits
} #}}} 

verify_quit() { #{{{
  local timeout=10
  echo "Press ctrl+c again within ${timeout} seconds to end script"
  sleep ${timeout}
  [[ $? -gt 0 ]] &amp;&amp; cleanup
} #}}}

cleanup() { #{{{
  exit 0
} #}}} 

initialize
while [ true ]
do 
  # do stuff
  sleep 10
done

#!/bin/bash

initialize() { #{{{

# Treat unset variables as an error

set -o nounset

trap verify_quit INT # verify ending script

trap cleanup TERM EXIT # clean up if script exits

} #}}}

verify_quit() { #{{{

local timeout=10

echo "Press ctrl+c again within ${timeout} seconds to end script"

sleep ${timeout}

[[ $? -gt 0 ]] && cleanup

} #}}}

cleanup() { #{{{

exit 0

} #}}}

initialize

while [ true ]

# do stuff

sleep 10

done

The initialize() and cleanup() are my usual function names I have in every script, making sure general settings and variables are defined and that on exit any tempfiles get deleted.
What has been added was a trap for the INT signal (ctrl+c) which calls the verify_quit() function, giving the user 10 seconds to press ctrl+c again to exit (via cleanup()) or return back to wherever we were in the code. There is one unavoidable caveat, the first ctrl+c will kill whatever the script was doing before it jumps into the verify_quit() function.