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Re: Why xargs still call the command when there is no input?
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From: |
Eric Blake |
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Subject: |
Re: Why xargs still call the command when there is no input? |
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Date: |
Tue, 02 Jun 2015 21:59:22 -0600 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 |
On 06/02/2015 04:02 PM, Peng Yu wrote:
> The following command will call ls. But since there is no input,
> shouldn't xargs quit without doing anything? Thanks.
>
> xargs -0 ls </dev/null
Try:
xargs -r -0 ls </dev/null
Per POSIX, the behavior of one-or-more (without -r) is required, to
match historical practice, and existing scripts rely on that behavior.
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/xargs.html
We have the -r extension precisely because sometimes the zero-or-more
behavior makes more sense.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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