Shell scripting: die on any error

Question

Suppose a shell script (/bin/sh or /bin/bash) contained several commands. How can I cleanly make the script terminate if any of the commands has a failing exit status? Obv

Answer 1

With standard sh and bash, you can

set -e

It will

$ help set
...
        -e  Exit immediately if a command exits with a non-zero status.

It also works (from what I could gather) with zsh. It also should work for any Bourne shell descendant.

With csh/tcsh, you have to launch your script with #!/bin/csh -e

Answer 2

May be you could use:

$ <any_command> || exit 1

Answer 3

You can check $? to see what the most recent exit code is..

e.g

#!/bin/sh
# A Tidier approach

check_errs()
{
  # Function. Parameter 1 is the return code
  # Para. 2 is text to display on failure.
  if [ "${1}" -ne "0" ]; then
    echo "ERROR # ${1} : ${2}"
    # as a bonus, make our script exit with the right error code.
    exit ${1}
  fi
}

### main script starts here ###

grep "^${1}:" /etc/passwd > /dev/null 2>&1
check_errs $? "User ${1} not found in /etc/passwd"
USERNAME=`grep "^${1}:" /etc/passwd|cut -d":" -f1`
check_errs $? "Cut returned an error"
echo "USERNAME: $USERNAME"
check_errs $? "echo returned an error - very strange!"