GNU bug report logs - #48329
The xargs -r, --no-run-if-empty Option Is Ignored When a Delimiter Is Passed

Previous Next

To add a comment to this bug, you must first unarchive it, by sending
a message to control AT debbugs.gnu.org, with unarchive 48329 in the body.
You can then email your comments to 48329 AT debbugs.gnu.org in the normal way.

Toggle the display of automated, internal messages from the tracker.

Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Kurt von Laven <kurt.von.laven <at> gmail.com>
To: bug-coreutils <at> gnu.org
Subject: The xargs -r,
 --no-run-if-empty Option Is Ignored When a Delimiter Is Passed
Date: Sun, 9 May 2021 23:04:50 -0700

[Message part 1 (text/plain, inline)]

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

[Message part 2 (text/html, inline)]

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.