[TIL] How to parse flags passed to a bash script

TIL how to parse flags passed to a bash script, using the built-in function getopts.

Let's say you have a script named maintenance.sh, to which you'd like to pass some flags:

• -e
• -d
• -f filename

These flags can be parsed in the script, like so:

while getopts edf: flag
do
    case "${flag}" in
        e) echo "Got flag -e";;
        d) echo "Got flag -d";;
        f) echo "Got flag -f with respective option ${OPTARG}";;
    esac
done

Notice in the arguments of getopts that f is the only flag that is followed by :, which is used to indicate that the flag is followed by a respective value.

Script can then be called as sh maintenance.sh -e or sh maintenance.sh -e -f file.json, for example.

See:

• How to Use Command Line Arguments in a Bash Script
• getopts man page