GNU bug report logs - #22656
How to grep two patterns in a line with correct coloring?

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Peng Yu <pengyu.ut <at> gmail.com>
To: bug-grep <at> gnu.org
Subject: How to grep two patterns in a line with correct coloring?
Date: Sat, 13 Feb 2016 18:10:01 -0600

Hi,

I know that I can use this to grep two patterns. But it can not
highlight both patterns.

grep word1 FILE | grep word2

Or I can use the following. But it is cumbersome as I have to type
word1 and word2 twice. And this method is not scale if I want grep
multiple patterns. The coloring can not be just for word1 and word2
only.

grep -E 'word1.*word2|word2.*word1' logs

Could anybody let me know what is the best way to grep two patterns in
a line with correct coloring? Thanks.

-- 
Regards,
Peng

Message #8 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Gary Johnson <garyjohn <at> spocom.com>
To: bug-grep <at> gnu.org
Subject: Re: bug#22656: How to grep two patterns in a line with correct
 coloring?
Date: Sat, 13 Feb 2016 18:28:37 -0800

On 2016-02-13, Peng Yu wrote:
> Hi,
> 
> I know that I can use this to grep two patterns. But it can not
> highlight both patterns.
> 
> grep word1 FILE | grep word2

This seems to work:

    grep --color=always word1 FILE | grep word2

Regards,
Gary

Message #13 received at 22656-done <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Peng Yu <pengyu.ut <at> gmail.com>
Cc: 22656-done <at> debbugs.gnu.org
Subject: Re: How to grep two patterns in a line with correct coloring?
Date: Sun, 10 Apr 2016 21:45:49 -0700

This works for me:

grep --color=always -E 'word1|word2'

Message #16 received at 22656 <at> debbugs.gnu.org (full text, mbox):

From: Zev Weiss <zev <at> bewilderbeest.net>
To: 22656 <at> debbugs.gnu.org, eggert <at> cs.ucla.edu, pengyu.ut <at> gmail.com
Subject: Re: bug#22656: How to grep two patterns in a line with correct
 coloring?
Date: Mon, 11 Apr 2016 00:39:00 -0500

On Sun, Apr 10, 2016 at 09:45:49PM -0700, Paul Eggert wrote:
>This works for me:
>
>grep --color=always -E 'word1|word2'
>

Isn't that a different search?  The original question asked about 
colorizing both patterns in the output of

 grep word1 | grep word2

(i.e. lines that contain *both* word1 and word2), whereas egrepping for 
'word1|word2' outputs lines that contain *either*.

Gary Johnson suggested

 grep --color=always word1 | grep word2

which seems like it should work in most cases, but would break down in 
cases where word2 overlaps a boundary of word1 (since the escape codes 
for colorizing the word1 match would throw off the matching of word2).  
So in full generality it seems like you'd have to do something like:

 grep word1 | grep word2 | grep -E 'word1|word2'

(so that the first two just filter and only the final one colorizes).

Granted,

 echo abc | grep -E --color 'ab|bc'

only colorizes the "ab" part of the output anyway (I'm assuming that's 
expected, and not itself a bug, but I'm not certain).


Zev

Message #19 received at 22656 <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Zev Weiss <zev <at> bewilderbeest.net>, 22656 <at> debbugs.gnu.org,
 pengyu.ut <at> gmail.com
Subject: Re: bug#22656: How to grep two patterns in a line with correct
 coloring?
Date: Sun, 10 Apr 2016 22:54:21 -0700

Zev Weiss wrote:
> The original question asked about colorizing both patterns in the output of
>
>   grep word1 | grep word2
>
> (i.e. lines that contain *both* word1 and word2)

I interpreted the original question the other way. Now that I reread it, it 
appears to be ambiguous.

This bug report does have the flavor of someone trying to use debbugs.gnu.org to 
solve a homework problem, which means I should probably stop now....

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