[bug #62043] The xargs -r, --no-run-if-empty Option Is Ignored When a Delimiter Is Passed

URL:
  <https://savannah.gnu.org/bugs/?62043>

                 Summary: The xargs -r,  --no-run-if-empty Option Is Ignored
When a Delimiter Is Passed
                 Project: findutils
            Submitted by: eggert
            Submitted on: Sat 12 Feb 2022 09:57:51 PM PST
                Category: xargs
                Severity: 3 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: Kurt von Laven
        Originator Email: 
             Open/Closed: Open
                 Release: None
         Discussion Lock: Any
           Fixed Release: None

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Details:

_I am filing this bug on behalf of Kurt von Laven, who mistakenly filed it as
Coreutils Bug 48329 <https://bugs.gnu.org/48329>. The rest of this bug report
is from Kurt._


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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