Commenting and large pipelines

[Zach Riggle <zachriggle@gmail.com>]

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Let's assume I have a series of large commands which need to be piped to
eachother.

Additionally, the pipeline itself must behave differently based on some
global flags or arguments.

There's a lot of way to make logic for this (e.g. functions), but one that
I've become a fan of is something like this below.

    cmd1=( some long command $FLAG bar baz )
    cmd2=( grep -E "$@" )
    cmd3=(
        grep
            -v # Don't match these
            -e 'fizz|buzz'
    )

    "${cmd1[@]}" | "${cmd2[@]}" | "${cmd3[@]}"

However, conditional logic makes this annoying and a bit opaque --
functions definitely excel here.

Another issue is that of adding comments to the arguments and the pipeline
itself -- lines that end with '\' cannot contain comments.  Functions
obviously can contain comments within themselves.

What I've discovered is that something like this works out pretty well...

    { printf "%s\n" a b foo c bar d fizz XfooX XbuzzX } |
    { grep -E 'foo|bar' } |
    {
        # If the user specified '--no-fizz-buzz', remove those entries
        if (( NO_FIZZ_BUZZ )); then
            grep -vE 'fizz|buzz'
        else
        # Pass through everything
            cat
        fi
    }

I have a few questions about this construct.

    1. Am I insane for doing this?
    2. In what ways is this a terrible idea?
    3. Is the use of {} better than ()?
    4. How much of a performance hit does this make, versus hand-writing a
different pipeline?
    5. Are there any ways to improve this?  For example, replacing 'cat' in
the default case.

Thanks for the attention, just curious what everybody thinks about this
abuse of pipelines and conditional logic.

*Zach Riggle*

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