Linux Pocket Guide, 2nd Edition

Exiting with a Return Code

The exit command terminates your script and passes a given return code to the shell. By tradition, scripts should return 0 for success and 1 (or other nonzero value) on failure. If your script doesn’t call exit, the return code is automatically 0.

if [ $# -lt 2 ]
then
  echo "$0 error: you must supply two arguments"
  exit 1
else
  echo "My name is $1 and I come from $2"
fi
exit 0

$ ./myscript Bob
./myscript error: you must supply two arguments
$ echo $?
1