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Colorize terminal text with regular expressions.

Project description

Colorize terminal text with regular expressions.


grec is similar to grep; the difference being that instead of printing matching lines in a file, grec colorizes lines. Lines that do not match any pattern are still printed, but without color.

The key feature that separates this utility from other similar ones is that it’s possible to colorize a matching string several times without letting previously matched colors mess up following regular expression matches.

Quick Start

Install with pip:

pip install grec

Print the contents of log_file.txt in its entirety but also colorize any occurrences of errors and warnings:

grec -m ERROR red -m WARN yellow log_file.txt

Or use a pipe:

cat log_file.txt | grec -m ERROR red -m WARN yellow -

To colorize strings in Python code, use the Matcher class from the grec package:

>>> from grec import Matcher
>>> m = Matcher()
>>> m.add_pattern('ERROR', 'red')
>>> m.add_pattern('WARN', 'yellow')
>>> print m.match('ERROR WARN INFO')
ERROR WARN INFO  (with color)

Command line

The command line interface is the following:

grec [-m PATTERN COLOR_INFO] [-g PATTERN [COLOR_INFO ...]] -- file

The -m argument

This argument takes a regular expression and color information. Here’s an example that will make all lines starting with the character “#” have a green color with white background:

-m '^#.*' green_on_white

Whenever a line matches the regular expression, the part of the line that matched is colorized with the color information. Any number of -m arguments can be specified, and colorization will be applied in the order specified on the command line.

The regular expression will be matched by the re module. So for each regular expression, only non-overlapping matches will be colorized. To get overlapping matches use several patterns by adding more -m arguments.

Color information consists of a foreground and optionally a background. Colorization is performed with the termcolor package and thus the following colors are supported: grey, red, green, yellow, blue, magenta, cyan, white.

To only set the foreground color, simply specify the name of the color. To also set a background color, add it to the foreground color. Use quotes or underlines to prevent the shell from interpreting it as several arguments. Examples:

-m <regex> blue_on_yellow
-m <regex> blue_yellow
-m <regex> 'blue on yellow'
-m <regex> 'blue yellow'

The -g argument

This argument is similar to -m but with the difference that instead of colorizing the whole match, this creates a group pattern that only colorizes matched groups of the regular expression.

Because one can have multiple groups within a regular expression, this argument accepts multiple colors. Here’s an example which will colorize the first group with green color on white background and the second with yellow foreground:

-g '^(#)(.*)' green_on_white yellow

If more colors than there are groups in the regular expression are specified, they will be ignored. If the number of colors is less than the groups, the last color specified for the pattern will be used to colorize all of the remaining group matches.

The file argument

This is the file to colorize. If “-” is specified, stdin will be read instead and can be used to colorize the output of a pipe.

If no file is given, stdin will be used as the default.


  • Add support for attributes like blinking

  • Add support for only changing background color from CLI

  • Python 3 support


0.2.0 (2014-10-14)

  • Added support for colorizing groups in regular expressions

0.1.0 (2014-09-26)

  • First release on PyPI.

Project details

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