Bash script must-haves

gistfile1.sh

# Taken from http://www.davidpashley.com/articles/writing-robust-shell-scripts.html

# abort when trying to use an unset variable
set -u # or set -o nounset

# exit on non-zero return codes from statements
# note: checking $? won't work any more, should use:
# command || { echo "command failed"; exit 1; }
set -e # or set -o errexit

# avoid race conditions
if ( set -o noclobber; echo "$$" > "$lockfile") 2> /dev/null; 
then
    trap 'rm -f "$lockfile"; exit $?' INT TERM EXIT

    # critical-section
   
    rm -f "$lockfile"
    trap - INT TERM EXIT # reset to the previous handler
else
    echo "Failed to acquire lockfile: $lockfile." 
    echo "Held by $(cat $lockfile)"
fi

# rollback handler in case of premature exits
rollback() {
    # do clean up
}
trap rollback INT TERM EXIT
# do something
trap - INT TERM EXIT