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If I use two consecutive grep commands, e.g.:

echo "foo bar" | grep foo | grep bar

Then the first pattern ("foo") is not highlighted. In fact, it seems that grep removes color codes from its input. Is there any way to prevent this?

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  • Another question with the same answer: how can you restore colored output to a grep within a bash function? Feb 6, 2019 at 20:31

1 Answer 1

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Use --color=always.

grep detects if output is to a pipe (or file). You most never want colors when output is to file – as that is escape sequences for the terminal. Typically:

foo ^[[01;31m^[[Kbar^[[m^[[K

from e.g.:

grep pattern file > result

To override use --color=always.

grep --color=always pattern file | ...

Example:

Having file:

ID=111;Year=2013;foo=bar
ID=222;Year=2013;foo=baz

Then

grep --color=always ID file | grep --color=always 2013 | grep foo

would color ID, 2013 and foo.

grep --color=always ID file | grep 2013 | grep foo

would color ID and foo, but not 2013.

1Important: You also have to remember that the added clutter from colors is passed to next command in the chain. Once ID is colored, you can't (with ease), match e.g. ID=111.


On some occasion one would perhaps want terminal colors in file. Try e.g.

 grep --color=always foo file > result
 cat result

Though the resulting file would have very limited portability.


The coloring itself is also an extension.


As mentioned by the good @slm, you could add:

export GREP_OPTIONS="--color=always"

to your .bashrc etc, but don't unless you for some reason really understand the implications and still want to do it. It would in many ways break grep due to the fact mentioned above 1.

Add an alias if you use it often.

 alias cgrep='grep --color=always'

GREP_OPTIONS and --color take three options: never, auto and always. The two first should be the only ones considered for GREP_OPTIONS.

You could also check out GREP_COLORS in the man pages or at gnu grep.

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  • Additional details on this methods pros/cons here: stackoverflow.com/questions/867877/…
    – slm
    May 12, 2013 at 15:46
  • 4
    add this to the answer too: export GREP_OPTIONS="--color=always" in a .bashrc makes the options the defaults for any greps, and you've pretty much nailed it!
    – slm
    May 12, 2013 at 15:53
  • Good stuff in this Super Uuser Q&A: superuser.com/questions/36022/…
    – slm
    May 12, 2013 at 15:54
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    export GREP_OPTIONS="--color=always" is deprecated (2019), and 'alias cgrep='grep --color=always''' isn't available inside bash functions.
    – mosh
    May 15, 2019 at 17:54
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    How do I make grep preserve colors from piped input and NOT add color to the match (i.e. only use grep to filter lines)?
    – geekley
    Nov 14, 2020 at 0:25

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