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Re: grep
From: |
Gaute B Strokkenes |
Subject: |
Re: grep |
Date: |
28 Jun 2001 10:54:36 +0100 |
User-agent: |
Gnus/5.090004 (Oort Gnus v0.04) Emacs/20.7 |
On Thu, 28 Jun 2001, address@hidden wrote:
> I found a bug in grep utility.
>
> I have a file which contains the following lines
>
> ------
> AS123
> FG32
> AS435
> -----
>
>
> no in command prompt I have given grep command like
>
> grep [^A] <file_name>
>
> I expect only FG32 to be displayed. but it out put was all contents
> of the file. why this behaviour is happening
Because you're asking grep to find lines which contain any character
that is not A.
You've misunderstood the meaning of "^". When at the very beginning
of the regexp, it means "this should be the very beginning of the
line". When it is the first character in a character class (a string
of characters enclosed by [ and ] ) then it means negation, i.e. all
characters that are not explicitly mentioned rather than just those
that are listed.
I hope that makes it clear; if not then please ask.
address@hidden:~$ cat > fubar
AS123
FG32
AS435
address@hidden:~$ grep ^A fubar
AS123
AS435
address@hidden:~$ grep [^A] fubar
AS123
FG32
AS435
address@hidden:~$
--
Big Gaute http://www.srcf.ucam.org/~gs234/
I want a VEGETARIAN BURRITO to go.. with EXTRA MSG!!
- grep, salil gk, 2001/06/28
- Re: grep,
Gaute B Strokkenes <=