Re: HELP: w/ grep on a log file.
On Sat, 13 Jun 1998, Johann Spies wrote:
> Hallo,
>
> Sorry if this bores you, but I have never used sed before and after
> reading this discussion I checked the man page for sed.
>
> What I would like to know is the following:
>
> On Fri, 12 Jun 1998, Steve Mayer wrote:
>
> > Try grep "`date \"+ %a %b %d\" | sed 's/ //'`" arch.log
> ^ ^
> > dave oswald wrote:
>
> > > grep echo \"`date "+ %a %b %d" | sed 's/ //'`\" arch.log
> ^ ^
> What is the meaning of the ` before date and after //'?
> What was wrong with dave oswald's effort?
My understanding is that commands between the (`)'s pass their output as
the parameter.
Try echo `hostname` or suchlike
> Why wouldn't
>
> grep \"`date "+ %a %b %d" | sed 's/ //'`\" arch.log
>
> work?
grep expects one string for its pattern input. enclosing it in quotes (")
makes it one string. using \" is an escape to tell grep to look for a " in
the file, but just " bounds the pattern to search for.
i.e.
grep "hello world" file
looks for the string 'hello world' in the file 'file' wheras:
grep \"hello world\" file
looks for the string '"hello' in the files 'world"' and 'file' and:
grep "\"hello world\"" file
looks for the string '"hello world"' in the file 'file'.
Hope that helps.
For all the grep gurus out there, correct me if I am wrong.. PLEASE!
Michael Beattie (mickyb@es.co.nz)
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