246

I use the --colour option of grep a lot, but I often use less as well. How can I pipe grep results to less and still preserve the coloring. (Or is that possible?)

grep "search-string" -R * --colour | less 

EDIT:

I'm looking for a direct solution or anything equivalent to this.

274

When you simply run grep --color it implies grep --color=auto which detects whether the output is a terminal and if so enables colors. However, when it detects a pipe it disables coloring. The following command:

grep --color=always -R "search string" * | less

Will always enable coloring and override the automatic detection, and you will get the color highlighting in less.

EDIT: Although using just less works for me, perhaps older version require the -R flag to handle colors, as therefromhere suggested.

  • 142
    You need to use less -R for the colour encoding to be interpreted by less correctly – therefromhere Sep 4 '09 at 23:24
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    It worked for me with just less, it may be version dependent. – drrlvn Sep 5 '09 at 12:14
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    A (hopefully) useful addendum: I needed to exclude some matches but maintain the colouring, so I actually ended up with grep pattern file | grep -v badpattern | grep --colour=always pattern | less -R, which met my needs perfectly. (Thanks again!) – Owen Blacker Mar 6 '12 at 15:35
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    I can't believe they just implemented the color-handling feature in less and therefore missed the chance to have a special colorless tool. For the name alone it should have been done! I should probably write a patch that invokes -R automatically when the binary is run as colorless. – Christian Jul 10 '13 at 0:42
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    @OwenBlacker It might not be an alias. You might have $LESS set with -R. – greyfade Aug 30 '16 at 21:01
27

You can put this in your .bashrc file:

export GREP_OPTIONS="--color=always"

or create an alias like this:

alias grepc="grep --color=always"

and you will need to use the -R option for less, as pointed out by therefromhere

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    Warning!: GREP_OPTIONS="--color=always" may break many scripts that use grep (or (e|f)grep). – mctylr Mar 12 '10 at 19:25
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    Yeah, better to just alias grep. You can always get pure grep with GREP, or override the --color option manually. – asmeurer Jul 18 '11 at 22:51
  • This doesn't work for me, alias does work though. – saeedgnu Feb 28 '14 at 3:30
9

In case like this, I prefer to actually create small sh files and put them on /usr/local/bin.
I usually use grep in the recursive way on the pwd, so thats my personal script:

#!/bin/sh
grep --color=always -r "$@" . | less -R

And then I've just copied it as /usr/local/bin/g (yes, I use it a lot)

  • 2
    Why not just use shell functions for this kind of thing? g() { grep --color=always -r "$@" . | less -R } works identically and probably will give (minutely) better performance. – 00dani Jan 11 '17 at 2:00
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    @00dani yeah, that's a valid alternative too and sometimes I use it. Please note that in this case, most time is spent in IO and therefore there is no perceivable performance boost :) Another difference is that once in your PATH, this script can be used with other shell scripts and aliases too; the function instead needs to be explicitly loaded – Iazel Jan 27 at 12:15
1

Don't alias "grep", better to alias "less" which is never used by shells. In your .bashrc just put: alias less="less -r".

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    Not quite right. One needs to use both grep --color=always and less -R. Note that grep only knows it is being piped into some other process and the --color=auto option uses solely this information to decide if will output colors or not. – brandizzi Apr 17 '13 at 18:35
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    Note that less option -r is different than -R. Probably -R is safer. – Craig McQueen Jan 9 '14 at 0:26
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    So why down-vote my solution. The OP specifically ask for less with the example already using `--color' option. – not2qubit Jan 9 '14 at 15:58
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    An alias is probably undesirable here. less supports a $LESS environment variable. So, instead of an alias, export LESS='-R' might be preferable. – greyfade Aug 30 '16 at 20:59
0

I need to run

grep --color=always -R "search string" * | less - r

with the -r flag after less, in order this to run.

  • What does * do? From the man page of grep: *: The preceding item will be matched zero or more times. But I still don't understand..! – Shayan Sep 1 at 17:36

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