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bug#20443: grep pattern is forward slash + star
From: |
Eric Blake |
Subject: |
bug#20443: grep pattern is forward slash + star |
Date: |
Mon, 27 Apr 2015 14:53:02 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 |
tag 20443 notabug
thanks
On 04/27/2015 01:05 PM, Clay Hansen wrote:
> Dear Coders,
>
> if I echo 'a * z' | grep '/*' it succeeds and prints 'a * z'.
> Can this be right?
Yes. The regular expression '/*' says to match 0-or-more instances of
'/'. 'a * z' has zero instances of '/', so it matches and gets printed.
>
> echo 'a * z' | grep -F '/*' fails as expected.
That's the literal pattern '/*', which does not appear in your input.
Remember, to convert the literal pattern of '/*' under -F to a regular
expression when not using -F, you must escape any characters that are
otherwise special to regular expressions. Your second command would be
equivalent to:
echo 'a * z' | grep '/\*'
where the '*' now matches a literal star rather than being the
0-or-more-operator.
As such, this is not a bug, so I'm closing the report. However, feel
free to ask further questions on the topic.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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