GNU bug report logs - #48329
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: 48329 <at> debbugs.gnu.org
Subject: bug#48329: The xargs -r, --no-run-if-empty Option Is Ignored When a Delimiter Is Passed
Date: Sun, 9 May 2021 23:04:50 -0700

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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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