GNU bug report logs - #48330
The xargs -r, --no-run-if-empty Option Is Ignored When a Delimiter Is Passed

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From: Kurt von Laven <kurt.von.laven <at> gmail.com>
To: 48330 <at> debbugs.gnu.org
Subject: bug#48330: The xargs -r, --no-run-if-empty Option Is Ignored When a Delimiter Is Passed
Date: Sun, 9 May 2021 23:07:18 -0700

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P.S. Apologies, the || in that last command should be a &&. Here is the
corrected command:

[[ $input = *[![:space:]]* ]] && xargs --null -I str echo str <<< "$input"

El dom, 9 may 2021 a las 23:04, Kurt von Laven (<kurt.von.laven <at> gmail.com>)
escribió:

> Hello,
>
> When the -r, --no-run-if-empty option is combined with the -d, --delimiter
> or -0, --null options, the -r, --no-run-if-empty option does not
> take effect. The manual describes the intended behavior of the -r,
> --no-run-if-empty option: "If the standard input does not contain any
> nonblanks, do not run the command.  Normally, the command is run once even
> if there is no input.  This option is a GNU extension."
>
> The following command correctly outputs nothing.
> xargs --no-run-if-empty -I str echo str <<< ""
>
> The following command incorrectly outputs 1 empty line.
> xargs --no-run-if-empty --delimiter="\n" -I str echo str <<< ""
>
> The following command incorrectly outputs 2 empty lines.
> xargs --no-run-if-empty --null -I str echo str <<< ""
>
> As a workaround according to this Stack Overflow answer
> <https://stackoverflow.com/a/17287097/3866835>, the following commands
> output nothing when the input consists only of whitespace.
> [[ $input = *[![:space:]]* ]] && xargs --delimiter="\n" -I str echo str
> <<< "$input"
> [[ $input = *[![:space:]]* ]] || xargs --null -I str echo str <<< "$input"
>
> Be well,
> Kurt von Laven
>

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