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Re: printf '%s\n' "$@" versus <<< redirection

From: Greg Wooledge
Subject: Re: printf '%s\n' "$@" versus <<< redirection
Date: Mon, 20 Feb 2023 07:42:19 -0500

On Mon, Feb 20, 2023 at 12:31:11PM +0000, goncholden wrote:
> Does the problem of disappearing variables exist in
> calls to awk ? 
> for arg in "$@"; do
>   printf '%s\n' "$arg" | awk '...'
> done

Both printf and awk will be executed in subshells.  However, awk is
already an external program, so it's *always* executed as a separate
process.  awk has its own variables which are never shared back to
the script from which you call it.

> or should one use 
> for arg in "$@"; do
>   awk '...' < <(printf '%s\n' "$arg")
> done

That wouldn't change anything.  awk is still an external program, and
is therefore still executed as a separate process, with its own private
variables and so on.

> There is also the possibility of putting the awk command in the process 
> substitution, not the printf command: 
> for arg in "$@"; do
>   while read ...; do
>     ...
>   done < <(awk '...' <<< "$arg")
> done

Without knowing what your awk command *does* it's hard to give advice,
but it might be more efficient if you call it once instead of once
per argument.

theone() {
    printf '%s\n' "$@" | awk 'whatever'

This is contingent upon your awk command being able to handle the full
input stream sent in this way.

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