Preserve colouring after piping grep to grep
There is a simlar question in Preserve ls colouring after grep’ing but it annoys me that if you pipe colored grep output into another grep that the coloring is not preserved.
As an example grep --color WORD * | grep -v AVOID
does not keep the color of the first output. But for me ls | grep FILE
do keep the color, why the difference ?
Solution 1:
grep
sometimes disables the color output, for example when writing to a pipe. You can override this behavior with grep --color=always
The correct command line would be
grep --color=always WORD * | grep -v AVOID
This is pretty verbose, alternatively you can just add the line
alias cgrep="grep --color=always"
to your .bashrc
for example and use cgrep
as the colored grep. When redefining grep
you might run into trouble with scripts which rely on specific output of grep
and don't like ascii escape code.
Solution 2:
A word of advice:
When using grep --color=always
, the actual strings being passed on to the next pipe will be changed. This can lead to the following situation:
$ grep --color=always -e '1' * | grep -ve '12'
11
12
13
Even though the option -ve '12'
should exclude the middle line, it will not because there are color characters between 1
and 2
.
Solution 3:
The existing answers only address the case when the FIRST command is grep
(as asked by the OP, but this problem arises in other situations too).
More general answer
The basic problem is that the command BEFORE | grep
, tries to be "smart" by disabling color when it realizes the output is going to a pipe. This is usually what you want so that ANSI escape codes don't interfere with your downstream program.
But if you want colorized output emanating from earlier commands, you need to force color codes to be produced regardless of the output sink. The forcing mechanism is program-specific.
Git: use -c color.status=always
git -c color.status=always status | grep -v .DS_Store
Note: the -c
option must come BEFORE the subcommand status
.
Others
(this is a community wiki post so feel free to add yours)