[Novalug] grep usage request
David Durant (emags)
emags4DLD@cox.net
Wed May 7 10:43:33 EDT 2014
On 05/07/2014 09:51 AM, Michael Henry wrote:
> On 05/07/2014 09:36 AM, Richard Rognlie wrote:
>> find /home/chowe -type f -print0 | xargs -0 grep "1Adam P" /dev/null
>>
>> Why do I have the /dev/null at the end, you ask?
> [...]
>> Sure, there's probably a cmdline switch in grep for that, but
>> I can never remember it.
Yes -- from the 'man grep' pages:
Output Line Prefix Control
-H, --with-filename
Print the file name for each match. This is the default
when there is more than one file to search.
-h, --no-filename
Suppress the prefixing of file names on output. This is
the default when there is only one file (or only standard input) to
search.
> With GNU xargs, you can avoid the case that grep will be invoked
> with no filename arguments via the -r (--no-run-if-empty) switch.
> >From man xargs:
>
> -r, --no-run-if-empty
> 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.
>
> find /home/chowe -type f -print0 | xargs -0r grep "1Adam P"
>
> Michael Henry
>
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