Friends don't let friends program in shell script

Lately I've been going over a hellish patch-work of old shell scripts we wrote to automate some internal processes and I realized something: friends shouldn't let friends program in shell script.

Why?

• Shell script is ugly.
• Shell script is unreliable.
• Shell script doesn't have exceptions.
• Shell script is hard to debug.
• Shell script is hard to test.
• Shell script isn't object oriented.
• Shell script is full of idiosyncratic cruft.
• Shell script doesn't have any decent data structures.
• Shell script doesn't scale.
• Shell script encourages code duplication.

The problem with shell script is that it's so deceptively easy to get started. Once you've started adding each bit of extra complexity seems easier than trashing the whole thing and starting from scratch in a decent language (e.g., Python) with a decent design.

Speaking from personal experience, nearly every time I have used shell script in recent times for something that isn't completely trivial, I have come to regret it. Ugh.

Sometimes you don't have a choice. For example, one time I had to use shell script to create a transparent command line hijacking function for a utility I was working on, and just look at the abomination I am ashamed to have been forced to write:

hijack_command() {
    CALLBACK=$1
    COMMAND=$2
    NEW_COMMAND=$3

    ORIG_COMMAND=$(which $COMMAND 2>/dev/null)

    eval "

        function $COMMAND() {
            args=()
            for arg; do
                args[\${#args[*]}]=\"'\$arg'\"
            done
            if $CALLBACK; then
                eval $NEW_COMMAND \${args[*]}
            else
                if [ \"$ORIG_COMMAND\" ]; then
                    eval $ORIG_COMMAND \${args[*]}
                fi
            fi
        }"
}

When a language forces you to do nested metaprogramming something as trivial as this, run and don't look back!

Have you ever regretted using shell script? Share your thoughts!