1

I'm learning Bash, and I've written a basic function:

wsgc () {
    # Wipe the global variable value for `getopts`.
    OPTIND=1;
    echo "git add -A";
    while getopts m:p option;
    do
        case "${option}"
        in
            m)
                COMMIT_MESSAGE=$OPTARG
                if [ "$COMMIT_MESSAGE" ]; then
                    echo "git commit -m \"$COMMIT_MESSAGE.\""
                else
                    echo "A commit message is required."
                    exit
                fi
                ;;
            p)
                echo "git push"
                exit
                ;;
            \?)
                echo "Invalid parameter."
                exit
                ;;
        esac
    done
}

However, I'm struggling with a couple of things:

  1. the if in m) isn't working, in that if I omit the argument, Bash intercedes and kicks me out of the session;

    git add -A
-bash: option requires an argument -- m
Invalid parameter.
logout
Saving session...
...copying shared history...
...saving history...truncating history files...
...completed.

    [Process completed]

  2. After running: wsgc -m "Yo!" -p, I get kicked out of the session.

    git add -A
git commit -m "Yo."
git push
logout
Saving session...
...copying shared history...
...saving history...truncating history files...
...completed.

    [Process completed]

Any advice would be much appreciated.

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2
  • 4
    return from a function, exit from a shell Commented Aug 31, 2017 at 21:17
  • @Kusalananda, obvious when you think about it, but that stopped the session killing behaviour. Commented Sep 1, 2017 at 7:00

2 Answers 2

Reset to default
2

the if in m) isn't working, in that if I omit the argument, Bash intercedes and kicks me out of the session;

You specify getopts m:p option. The : after the m means that you need an argument. If you don't provide it, it's an error.

After running: wsgc -m "Yo!" -p, I get kicked out of the session.

What do you mean by you get kicked out of the session? Does the shell vanish? Then that is because you sourced the script instead of executing it.

That being said, I would highly recommend to use getopt instead of getopts.

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2
  • I tried getopt but it triggered a loop, spewing out instances of --option. Commented Sep 1, 2017 at 6:59
  • "What do you mean by you get kicked out of the session?" See the output beneath each of the points I made. @Kusalananda helped me fix that with return instead of exit. Commented Sep 1, 2017 at 7:01
1
  • If the -m option don't get a value, you exit from the shell.
  • If you use the -p option, you exit from the shell.
  • If you use an invalid option, you exit from the shell.

In all those cases, you should return rather than exit, and in all cases except for the second, you should return 1 (to signal an error). Also, the error messages ought to be redirected to the standard error stream with >&2.

Here is a version of your function with some modifications that makes it not output anything unless the command line parsing went well.

wsgc () {
    local OPTIND=1
    local out=( "git add -A" )

    while getopts 'm:p' opt; do
        case "$opt" in
            m)  out+=( "git commit -m '$OPTARG'" ) ;;
            p)  out+=( 'git push' ) ;;
            *)  return 1 ;;
        esac
    done

    printf '%s\n' "${out[@]}"
}

If you need to impose an ordering of the output (the git push will only be the last thing outputted if -p is last on the command line with the above function), then use flags. This will also not output multiple commands if an option is used multiple times.

wsgc () {
    local OPTIND=1

    local message
    local do_push=0

    while getopts 'm:p' opt; do
        case "$opt" in
            m)  message="$OPTARG" ;;
            p)  do_push=1 ;;
            *)  return 1 ;;
        esac
    done

    local out=( "git add -A" )

    if [[ -n "$message" ]]; then
        out+=( "git commit -m '$message'" )
    fi

    if (( do_push )); then
        out+=( 'git push' )
    fi

    printf '%s\n' "${out[@]}"
}

That last bit of the function could be shortened to

local out=( "git add -A" )

[[ -n "$message" ]] && out+=( "git commit -m '$message'" )
(( do_push ))       && out+=( 'git push' )

printf '%s\n' "${out[@]}"
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  • It's a shame I can't split the accepted answer in two, because you both helped! Commented Sep 1, 2017 at 7:02

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