Removing ANSI color codes from text stream

Question

Examining the output from

perl -e 'use Term::ANSIColor; print color "white"; print "ABC\n"; print color "reset";'

in a text editor (e.g., vi) shows the following:

^[[37mABC
^[[0m

How would one remove the ANSI color codes from the output file? I suppose the best way would be to pipe the output through a stream editor of sorts.

The following does not work

perl -e 'use Term::ANSIColor; print color "white"; print "ABC\n"; print color "reset";' | perl -pe 's/\^\[\[37m//g' | perl -pe 's/\^\[\[0m//g'

Answer 1

The characters ^[[37m and ^[[0m are part of the ANSI escape sequences (CSI codes).  See also these specifications.

Using GNU sed

sed -e 's/\x1b\[[0-9;]*m//g'

• \x1b (or \x1B) is the escape special character
  (GNU sed does not support alternatives \e and \033)
• \[ is the second character of the escape sequence
• [0-9;]* is the color value(s) regex
• m is the last character of the escape sequence

Using the macOS default sed

Mike suggests:

sed -e $'s/\x1b\[[0-9;]*m//g'

The macOS default sed does not support special characters like \e as pointed out by slm and steamer25 in the comments.

To install gsed.

brew install gnu-sed

Example with OP's command line

_{(OP means Original Poster)}

perl -e 'use Term::ANSIColor; print color "white"; print "ABC\n"; print color "reset";' | 
      sed 's/\x1b\[[0-9;]*m//g'

Improvements

Flag -e is optional for GNU sed but required for the macOS default sed:

sed 's/\x1b\[[0-9;]*m//g'           # Remove color sequences only

Tom Hale suggests to also remove all other escape sequences using [a-zA-Z] instead of just the letter m specific to the graphics mode escape sequence (color):

sed 's/\x1b\[[0-9;]*[a-zA-Z]//g'    # Remove all escape sequences

But [a-zA-Z] may be too wide and could remove too much. Michał Faleński and Miguel Mota propose to remove only some escape sequences using [mGKH] and [mGKF] respectively.

sed 's/\x1b\[[0-9;]*[mGKH]//g'      # Remove color and move sequences
sed 's/\x1b\[[0-9;]*[mGKF]//g'      # Remove color and move sequences
sed 's/\x1b\[[0-9;]*[mGKHF]//g'     # Remove all

Last escape
sequence
character   Purpose
---------   -------------------------------
m           Graphics Rendition Mode (including color)
G           Horizontal cursor move
K           Horizontal deletion
H           New cursor position
F           Move cursor to previous n lines

Britton Kerin indicates K (in addition to m) removes the colors from gcc error/warning. Do not forget to redirect gcc 2>&1 | sed....

Using perl

The version of sed installed on some operating systems may be limited (e.g. macOS). The command perl has the advantage of being generally easier to install/update on more operating systems. Adam Katz suggests to use \e (same as \x1b) in PCRE.

Choose your regex depending on how much commands you want to filter:

perl -pe 's/\e\[[0-9;]*m//g'          # Remove colors only
perl -pe 's/\e\[[0-9;]*[mG]//g'
perl -pe 's/\e\[[0-9;]*[mGKH]//g'
perl -pe 's/\e\[[0-9;]*[a-zA-Z]//g'
perl -pe 's/\e\[[0-9;]*m(?:\e\[K)?//g' # Adam Katz's trick

Example with OP's command line:

perl -e 'use Term::ANSIColor; print color "white"; print "ABC\n"; print color "reset";' \
      | perl -pe 's/\e\[[0-9;]*m//g'

Usage

As pointed out by Stuart Cardall's comment, this sed command line is used by the project Ultimate Nginx Bad Bot (1000 stars) to clean up the email report ;-)

Answer 2

I have found out a better escape sequence remover if you're using MacOS. Check this:

perl -pe 's/\x1b\[[0-9;]*[mG]//g'

Answer 3

ansi2txt

https://unix.stackexchange.com/a/527259/116915

cat typescript | ansi2txt | col -b

• ansi2txt: remove ANSI color codes
• col -b: remove ^H or ^M

---

update: about col handle tabs and space //mentioned by @DanielF

〇. about col handle spaces and tabs

col -bx replace '\t' to ' ', col -bh replace ' ' to '\t'.

// seems col can't keep space/tabs as it is, it's a pity.

0. orig string

$ echo -e '        ff\tww' | hd
00000000  20 20 20 20 20 20 20 20  66 66 09 77 77 0a        |        ff.ww.|

1. -h repace spaces to tab

$ echo -e '        ff\tww' | col -b | hd
00000000  09 66 66 09 77 77 0a                              |.ff.ww.|
$ echo -e '        ff\tww' | col -bh | hd
00000000  09 66 66 09 77 77 0a                              |.ff.ww.|
$ echo -e '        ff\tww' | col -bxh | hd
00000000  09 66 66 09 77 77 0a                              |.ff.ww.|

2. -x repace tab to spaces

$ echo -e '        ff\tww' | col -bx | hd
00000000  20 20 20 20 20 20 20 20  66 66 20 20 20 20 20 20  |        ff      |
00000010  77 77 0a                                          |ww.|
$ echo -e '        ff\tww' | col -bhx | hd
00000000  20 20 20 20 20 20 20 20  66 66 20 20 20 20 20 20  |        ff      |
00000010  77 77 0a                                          |ww.|

3. seems col can't keep spaces and tabs as it is.

Answer 4

If you prefer something simple, you could use my strip-ansi-cli package (Node.js required):

$ npm install --global strip-ansi-cli

Then use it like this:

$ strip-ansi < colors.o

Or just pass in a string:

$ strip-ansi '^[[37mABC^[[0m'

Answer 5

What is displayed as ^[ is not ^ and [; it is the ASCII ESC character, produced by Esc or Ctrl[ (the ^ notation means the Ctrl key).

ESC is 0x1B hexadecimal or 033 octal, so you have to use \x1B or \033 in your regexes:

perl -pe 's/\033\[37m//g; s/\033[0m//g'

perl -pe 's/\033\[\d*(;\d*)*m//g'

Answer 6

A more thorough removal for ANSI escape sequences (not 100% comprehensive; see below):

perl -pe '
  s/\e\[[\x30-\x3f]*[\x20-\x2f]*[\x40-\x7e]//g;
  s/\e[PX^_].*?\e\\//g;
  s/\e\][^\a]*(?:\a|\e\\)//g;
  s/\e[\x40-\x5f]//g;'

(Please note that perl, like many other languages (but not sed), accepts \e as the escape character Esc, \x1b or \033 by code, shown in terminals as ^[. I'm using it here because it seems more intuitive.)

This perl command, which you can run all on one line if you prefer, has four replacements in it:

The first goes after CSI sequences (escape code sequences that begin with the "Control Sequence Introducer" of Esc[, which covers a lot more than the Select Graphic Rendition sequences that make up the color codes and other text decorations).

The second replacement removes the remaining sequences that involve trailing characters and terminate with ST (the String Terminator, Esc\). The third replacement is the same thing but also allows Operating System Command sequences to end with a BEL (\x07, \007, often \a).

The fourth replacement removes the remaining escapes.

Also consider removing other zero-width ASCII characters such as BEL and other more obscure C0 and C1 control characters. I've been using s/[\x00-\x1f\x7f-\x9f\xad]+//g, which also includes Delete and Soft Hyphen. This excludes Unicode's higher coded zero-width characters but I believe it's exhaustive for ASCII (Unicode \x00-\xff). If you do this, remove these last since they can be involved in longer sequences.

---

I recently translated this to native zsh. This implementation enables extendedglob and then disables it (if it wasn't already enabled) to respect your other items.

# Usage: remove_ansi STRING
remove_ansi() {
  local i ext= esc=$'\e' bel=$'\a'
  [[ -o extendedglob ]] && ext=1
  set -o extendedglob
  i="${*//$esc\[[0-?]#[ -\/]#[@-~]/}"     # no CSI seqs (colors, SGR, +)
  i="${(S)i//$esc[PX^_]#$esc\\/}"         # no ESC...ST seqs, (S) = lazy
  i="${i//$esc\][^$bel]#($bel|$e\\)/}"    # OS command seq ending in bell
  i="${i//$esc[A-_@]/}"                   # remove remaining ESC seqs
  i="${i//$bel/}"                         # remove remaining bells
  [[ -z "$ext" ]] && set +o extendedglob  
  echo "$i"
}

Each replacement is the equivalent of the same perl replacement, with the fifth being just for bells.

Key syntax to note:

• You can't use character escapes (\e or \033, etc) so I set up $esc and $bel to insert
• # is the same as * in regex: zero or more of the previous character/class/group
• (S) makes ranges lazy (non-greedy), so # is the same as *? in PCRE

More pointers at What kind of patterns can I use in zsh parameter expansion? and of the zsh docs for expansion.

Answer 7

commandlinefu gives this answer which strips ANSI colours as well as movement commands:

sed "s,\x1B\[[0-9;]*[a-zA-Z],,g"

For just colours, you want:

 sed "s,\x1B\[[0-9;]*m,,g"

Answer 8

There's also a dedicated tool for the job: ansifilter. Use the default --text output format.

ref: https://stackoverflow.com/a/6534712

Answer 9

The "answered" question didn't work for me, so I created this regex instead to remove the escape sequences produced by the perl Term::ANSIColor module.

cat colors.o | perl -pe 's/\x1b\[[^m]+m//g;

Grawity's regex should work fine, but using +'s appears to work ok too.

Answer 10

"tput sgr0" left this control character ^(B^[
Here is a modified version to take care of that.

perl -pe 's/\e[\[\(][0-9;]*[mGKFB]//g' logfile.log

Answer 11

Combining @Adam-Katz @Mike answers I get:

sed -E $'s|\x1b\\[[0-\\?]*[ -/]*[@-~]||g;
         s|\x1b[PX^_][^\x1b]*\x1b\\\\||g;
         s:\x1b\\][^\x07]*(\x07|\x1b\\\\)::g;
         s|\x1b[@-_]||g'

This should work on macos, linux, and mingw64x (Git for Windows)

Note: On super old GNU sed (pre 4.2), the -E flag needs to be replaced with -r (like CentOS 6.0 old)

Explanation of regexs

1st: An ANSI CSI Code consists of (in order)

1. One \x1b
2. One [
3. Zero or more parameter bytes 0x30-0x3f
4. Zero or more intermediate bytes 0x20-0x2f
5. One final byte 0x40-0x7f

2nd and 3rd: I'm unfamiliar with with in practice, but have read about them in the linked page.

4th: Just a catch all to get all remaining escape codes, assuming there are zero extra bytes. As these codes could do anything they want, it's possible data bytes get left behind, but extremely unlikely as they aren't used much in practice.

Answer 12

Python port of Adam Katz's excellent and comprehensive perl answer:

    def escape_ansi(line):
        re1 = re.compile(r'\x1b\[[\x30-\x3f]*[\x20-\x2f]*[\x40-\x7e]')
        re2 = re.compile(r'\x1b[PX^_].*?\x1b\\')
        re3 = re.compile(r'\x1b\][^\a]*(?:\a|\x1b\\)')
        re4 = re.compile(r'\x1b[\[\]A-Z\\^_@]')
        # re5: zero-width ASCII characters
        # see https://superuser.com/a/1388860
        re5 = re.compile(r'[\x00-\x1f\x7f-\x9f\xad]+')

        for r in [re1, re2, re3, re4, re5]:
            line = r.sub('', line)

        return line

This includes the C0/C1 sequence removal, so remove that if you don't need it. I realize this is not optimized since it's multiple regex passes, but it did the trick for me and optimization wasn't a concern for me.

Answer 13

I had similar problem with removing characters added from collecting interactive top output via putty and this helped:

cat putty1.log | perl -pe 's/\x1b.*?[mGKH]//g'

Answer 14

This is what worked for me (tested on Mac OS X)

perl -pe 's/\[[0-9;]*[mGKF]//g'

Answer 15

I've had to look this up too many times, so I decided to make a free online tool for it. No need to remember sed commands for this!

Hope it works well for you, too: https://maxschmitt.me/ansistrip/

Answer 16

This simple awk solution worked for me, try this:

str="happy $(tput setaf 1)new$(tput sgr0) year!"; #colored text
echo $str | awk '{gsub("(.\\[[0-9]+m|.\\(..\\[m)","",$0)}1'; #remove ansi colors

Answer 17

Also consider using the colorstrip function from this module.

colorstrip(STRING[, STRING ...]) colorstrip() removes all color escape sequences from the provided strings, returning the modified strings separately in array context or joined together in scalar context. Its arguments are not modified.

Answer 18

I know there have been many answers on how to deal with the situation once you have files with those characters in it. @oHo answer help me a lot with those.

Problem:

cat sometext.txt > ansi_codes_in_file.txt

In case anyone else have the same root cause issue, where cat outputs properly to the STDOUT (with colors) but it writes the ANSI Color Codes to file and you want to avoid that completely, this is what worked for me:

I had to review my .bashrc and .bash_profile files and found that my .bash_profile had the following line:

export GREP_OPTIONS='--color=always'

After seeing this answer: Different results in grep results when using --color=always option

Never use --color=always, unless you know the output is expected to contain ANSI escape sequences - typically, for human eyeballs on a terminal.

If you're not sure how the input is processed, use --color=auto, which - I believe - causes grep to apply coloring only if its stdout is connected to a terminal.

It was clear that I needed to change that in my .bash_profile to:

export GREP_OPTIONS='--color=auto'

After updating my .bash_profile and loading the config into my terminal (source ~/.bash_profile) doing the following works without ANSI Codes in the output file

cat sometext.txt > no_ansi_codes_in_file.txt

Note:

• In my case, I didn't have any alias set to my cat command