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According to the man page, xargs will quit if one of the execution lines exits with an error of 255:

If any invocation of the command exits with a status of 255, xargs will stop immediately without reading any further input. An error message is issued on stderr when this happens.

How can I get xargs to not do this?

I have a 1500 or so line batch job that I want to run, 50 lines at a time. I was finding that it was always dying at a certain line, and not completing the job. Not good!

An even better question, the question describing what I am trying to do, is:

How can I run a 1500 line batch script, 50 lines at a time, so that it does not quit the job in the middle, and so that the output is captured to a log file of some kind?

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up vote 0 down vote accepted

You could wrap the perl script with another simple bash script:

#!/bin/bash
real-command "$@" || exit 0

This will call real-command passing it all the parameters that you pass to this fake-command and it will always return a 0 exit code (that means it is always successful) and xargs will never stop with this.

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You could write your xargs invocation to mask the return codes of your command lines. With something like the following,xargs will never see exit codes return by somecommand:

xargs sh -c "somecommand || :"
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I've come up with a good solution: make sure the commands being processed do not exit with a 255 status! Additional Details The command being processed is a Perl script. The Perl die() function was being used in several places to exit out if some critical error occurred (e.g. could not connect to a database). However, die() always exits with error status 255. The solution in this case was to replace die() with a combination of print and exit(), along with a more reasonable error code ("1" worked in this case). – JDS Jul 11 '11 at 16:19

Similar to larsks answer but more explicit:

xargs sh -c "somecommand || true"
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Just found a fun answer to this one, though its usefulness will depend on the command you're trying to run.

If you're using xargs to basically assemble a list of commands, you can get this behavior by telling xargs to echo the command, then piping to bash.

For example, if you're trying to delete a list of things that may or may not exist:

# presume this will fail in a similar way to your command
cat things_to_delete | xargs -n1 delete_command_that_might_exit

# instead echo the commands and pipe to bash
cat things_to_delete | xargs -n1 echo delete_command_that_might_exit | bash

This works because, first, xargs is only ever calling echo, so it won't see any errors. Then second, because bash's default behavior to continue execution after a failed statement.

To be more specific about my case, I was using this to remove a bunch of old application versions from AWS ElasticBeanstalk like so:

aws elasticbeanstalk describe-application-versions --application-name myapp |\
jq -r '.ApplicationVersions | sort_by(.DateCreated) | .[0:-10] | .[].VersionLabel' |\
xargs -n1 \
  echo aws elasticbeanstalk delete-application-version \
       --delete-source-bundle --application-name myapp --version-label |\
bash
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Following construction works for me:

ls | xargs -I % svn upgrade %

Even if svn upgrade failed on some element, process was continued

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If you were using xargs with find, use the -exec option of find instead:

find . -name '*.log' -exec somecommand {} \;
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howdy. i could use that but the -exec option doesn't parallelize operations the way using xargs can and does – JDS Oct 23 '14 at 14:52
    
Thank you -- I didn't know that xargs could run commands in parallel. Cool. If you only want to minimize the number of command invocations, -exec has a + parameter. – Roger Dahl Oct 23 '14 at 15:05

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