Standard for ANSI Colors in Terminals

The current situation to get colored output from most console commands is a mess. Some check for the TERM environment variable, or look for ANSICON on Windows, or need to be passed a parameter like --color, --ansi or -fdiagnostics-color.

That’s why this page tries to create some sort of “standard” which programs should comply to no matter on which platform they are run.

The idea is to have the environment variables NO_COLOR, CLICOLOR_FORCE, and CLICOLOR (which are currently already used for this exact reason on some UNIX systems). When set, the following rules should apply:

NO_COLOR set
- Don’t output ANSI color escape codes, see no-color.org
CLICOLOR_FORCE set, but NO_COLOR unset
- ANSI colors should be enabled no matter what
CLICOLOR set, NO_COLOR and CLICOLOR_FORCE unset
- ANSI colors are supported and should be used when the program is writing to a terminal
none of the above environment variables are set
- ANSI colors are not explicitly requested
- Older programs newly gaining colors may prefer to disable them by default
- New programs may prefer to operate as if CLICOLOR is set

If you have ideas or comments please create a new issue on GitHub or edit this page.

How to Implement

If you want to check in your program if ANSI colors are supported, it should look like this Python code example:

import os, sys

def has_colors():
    if os.environ.get('NO_COLOR'):
        return False
    elif os.environ.get('CLICOLOR_FORCE'):
        return True
    return sys.stdout.isatty()

Python code example with CLICOLOR for auto-detection:

import os, sys

def has_colors():
    if os.environ.get('NO_COLOR'):
        return False
    elif os.environ.get('CLICOLOR_FORCE'):
        return True
    elif os.environ.get('CLICOLOR'):
        return sys.stdout.isatty()
    else
        return False

Also consider letting the user override these with command-line options like --color and --color=WHEN where WHEN would be one of:

--color or --color=always or --color=on: like CLICOLOR_FORCE
--color=never or --color=no: like NO_COLOR, a good default for software newly gaining colors
--color=auto: like CLICOLOR, a good default for newer software

Supported Colors

To get an idea what colors you can use, run the following Python script:

RESET = "\x1b[0m"
print("To reset attributes: \\x1b[0m\n")
for i in range(0, 8):
    print("\x1b[1;3{0}m\\x1b[1;3{0}m{1} \x1b[0;3{0}m\\x1b[0;3{0}m{1} "
          "\x1b[1;4{0};3{0}m\\x1b[1;3{0};4{0}m{1}".format(i, RESET))

Which should print:

To reset attributes: \x1b[0m

\x1b[1;30m \x1b[0;30m \x1b[1;30;40m
\x1b[1;31m \x1b[0;31m \x1b[1;31;41m
\x1b[1;32m \x1b[0;32m \x1b[1;32;42m
\x1b[1;33m \x1b[0;33m \x1b[1;33;43m
\x1b[1;34m \x1b[0;34m \x1b[1;34;44m
\x1b[1;35m \x1b[0;35m \x1b[1;35;45m
\x1b[1;36m \x1b[0;36m \x1b[1;36;46m
\x1b[1;37m \x1b[0;37m \x1b[1;37;47m

Also see the ISO 6429 (ANSI) color sequences.

Windows

Windows 10 supports ANSI colors since v1511. For earlier versions of Windows installing ANSICON will enable ANSI colors in cmd.exe.

Bug Reports

This is a list of bug reports on the progress of supporting CLICOLOR_FORCE:

The following bug reports have been resolved: