From: Philip Guenther <guenther@gmail.com>
Subject: Re: check_sym: do not run output commands twice
To: Christian Weisgerber <naddy@mips.inka.de>
Cc: Philip Guenther <guenther@openbsd.org>, tech@openbsd.org
Date: Mon, 11 May 2026 16:18:52 -0700

ok guenther@

On Mon, May 11, 2026 at 4:06 PM Christian Weisgerber <naddy@mips.inka.de> wrote:
>
> src/lib/check_sym has a function output_if_not_empty() that wraps
> the output of some command, but only if there is any.  To do this,
> it runs the command, checks if there is any output, then RUNS IT
> AGAIN.
>
> Ewww.
>
> The good news is that we can achieve the same by piping whatever
> output there is through a single sed invocation.  The addresses 1
> and $ only trigger if there is any input.
>
> The bad news, well, it's sed.
>
> OK?
>
> -----------------------------------------------
> commit 2efd5e35040658fa02336c5633ab824c84ddc081 (local)
> from: Christian Weisgerber <naddy@mips.inka.de>
> date: Mon May 11 22:44:05 2026 UTC
>
>  check_sym: do not run output commands twice
>
> diff cbfc2be66f713e85e01430423dcb36ac0c25092f 2efd5e35040658fa02336c5633ab824c84ddc081
> commit - cbfc2be66f713e85e01430423dcb36ac0c25092f
> commit + 2efd5e35040658fa02336c5633ab824c84ddc081
> blob - e51de0d98e481c487338ff0214331b0d1c3eda5f
> blob + 20ce3a47ca937b74308eb9067b091271a1f7cb1e
> --- lib/check_sym
> +++ lib/check_sym
> @@ -130,12 +130,13 @@ output_if_not_empty()
>  {
>         leader=$1
>         shift
> -       if "$@" | grep -q .
> -       then
> -               echo "$leader"
> -               "$@" | sed 's:^:        :'
> -               echo
> -       fi
> +       "$@" | sed '
> +1i\
> +'"$leader"'
> +s:^:   :
> +$a\
> +
> +'
>  }
>
>
>
> --
> Christian "naddy" Weisgerber                          naddy@mips.inka.de
>