Preserve colouring after piping grep to grep

linux bash colors grep pipe
Zitrax picture Zitrax · Feb 24, 2010 · Viewed 34k times · Source

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 ?

Answer

Otto Allmendinger picture Otto Allmendinger · Feb 24, 2010

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.

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