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How to handle color codes when trying to use grep, sed, etc.

I am trying to use sed to handle some output from a command that generates colored lines (this is git diff, but I don't think it matters). I am trying to match the “+” sign at the beginning of the line, but this mixes up with the color code that precedes the “+”. Is there an easy way to deal with this problem or do I need to use some kind of complex regular expression to match the color code.

If possible, I would like to keep the line coloring.

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linux unix bash grep sed
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3 answers

If you have to have coloring, you have to do something ugly:

$ git diff --color web-app/db/schema.rb |grep '^^[\[32m+

This ^[ is actually a raw escape character ( Ctrl + V ESC in bash, ASCII 27). You can use cat -v to determine the required escape sequences:

 $ git diff --color web-app/db/schema.rb |cat -v ^[[1mdiff --git a/web-app/db/schema.rb b/web-app/db/schema.rb^[[m ^[[1mindex 45451a2..411f6e1 100644^[[m ^[[1m--- a/web-app/db/schema.rb^[[m ^[[1m+++ b/web-app/db/schema.rb^[[m ...

Such things will work fine with versions of GNU sed , awk , ... YMMV with versions other than GNU.

An easier way is to rotate the coloring:

 $ git diff --no-color file

But you can trade nice results for slightly ugly regular expressions.

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There is really no need to deal with ugly regular expressions. You can simply pass the config variable to the git command that you use to maintain color.

 git -c color.diff=always diff | cat

This also works for git status

 git -c color.status=always status -sb | cat
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That ugly expression should do it

git diff --color src/Strmrs.h| grep $'^\(\x1b\[[0-9]\{1,2\}m\)\{0,1\}+'

  • $'...' will make the \ x1b character an ESC character (aka ^[ ) - this can probably be avoided, I was too lazy to read manpage
  • the color sequence (ESC, left bracket, 1-2 digits and the letter m ) is enclosed in an external set of \(\) , which then become optional with \{0,1\} , the only optional element is last + .
  • It is assumed that at the beginning of the line no more than one color sequence
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