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From: kaushal on 8 Jun 2010 10:45
Hi,

can someone explain me about the usage of grep , fgrep and egrep with
examples.
In what contexts i should use this.

Please guide/suggest

Thanks and Regards,

Kaushal
From: Teemu Likonen on 8 Jun 2010 10:50
* 2010-06-08 07:45 (-0700), kaushal wrote:

> can someone explain me about the usage of grep , fgrep and egrep with
> examples. In what contexts i should use this.

Start with this command:

$ man grep

Or read the manual of GNU grep from here:

http://www.gnu.org/software/grep/manual/html_node/index.html

(There are examples too.)
From: Ed Morton on 8 Jun 2010 12:06
On Jun 8, 9:45 am, kaushal <kaushalshri...(a)gmail.com> wrote:
> Hi,
>
> can someone explain me about the usage of grep , fgrep and egrep with
> examples.
> In what contexts i should use this.
>
> Please guide/suggest
>
> Thanks and Regards,
>
> Kaushal

Use grep to find text in a file, e.g.

$ cat file
here
is
some
text
$ grep "so" file
some

I wouldn't bother with fgrep or egrep. If you have to do anything more
complicated than that you may as well learn sed or awk as, with the
exception of a couple of cute GNU grep extensions, their syntax is as
simple as greps for what grep does but they're extensible to do things
grep can't do. The most extensible with the simplest syntax for
anything even moderately complex is awk but sed is also very useful
for simple searching/subsitutions on a single line.

Ed.
From: Kenny McCormack on 8 Jun 2010 12:40
In article <d8cbd965-3be1-4c65-b97f-b1a17072227a(a)y11g2000yqm.googlegroups.com>,
Ed Morton <mortonspam(a)gmail.com> wrote:
....
>I wouldn't bother with fgrep or egrep. If you have to do anything more
>complicated than that you may as well learn sed or awk as, with the
>exception of a couple of cute GNU grep extensions, their syntax is as
>simple as greps for what grep does but they're extensible to do things
>grep can't do. The most extensible with the simplest syntax for
>anything even moderately complex is awk but sed is also very useful
>for simple searching/subsitutions on a single line.

I agree with your general sentiment, and also your recommendation of AWK
(as the best balance between high level and low level). I disagree with
the (tepid) recommendation of sed - I find that once one knows AWK, sed
drops off the radar.

But, having said that, the fact is, this is comp.unix.shell, and one of
the groupthink principles of this newsgroup is that you *should* learn the
plethora of tools (join, comm, pr, sed, etc) and use them all. Also,
all the shell built-ins, like "read", etc.

Finally, my guess at the underlying meaning of the OP is that he is
dealing with existing code and/or a corporate situation where knowing
all these obscure tools is going to be necessary for him to work. I
know that in one of my former jobs, a lot of the existing shell codebase
used all these tools (join, comm, pr, sed, etc) to do things that could
have been done much more easily with a single, unified AWK script. But
ya gotta deal...

--
> No, I haven't, that's why I'm asking questions. If you won't help me,
> why don't you just go find your lost manhood elsewhere.

CLC in a nutshell.

From: Janis Papanagnou on 8 Jun 2010 13:24
kaushal wrote:
> Hi,
>
> can someone explain me about the usage of grep , fgrep and egrep with
> examples.
> In what contexts i should use this.

grep - if you're using simple regexps
fgrep - if you use literal strings
egrep - if you use extended regexps

Some samples to illustrate...

echo 'xyz' | grep x.z
echo 'xyz' | fgrep x.z

echo 'hello' | grep 'hello|world'
echo 'hello' | egrep 'hello|world'

And of course, as already proposed, man grep is your friend.

Janis

>
> Please guide/suggest
>
> Thanks and Regards,
>
> Kaushal
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