Posted 16 days ago. Visible to the public.

Bash: How to use colors in your tail output

Sometimes it's nice to have some coloring in your logs for better readability. You can output your logs via tail and pipe this through sed to add ANSI color annotations (which your console then interprets).

To print a log (e.g. rails log) and color all lines containing "FATAL" in red and all lines with "INFO" in green:

Copy
tail -f /path/to/log | sed --unbuffered -e 's/\(.*INFO.*\)/\o033[32m\1\o033[39m/' -e 's/\(.*FATAL.*\)/\o033[31m\1\o033[39m/'

Here are the most common color codes:

Color Font Background
Black \033[30m \033[40m
Red \033[31m \033[41m
Green \033[32m \033[42m
Orange \033[33m \033[43m
Blue \033[34m \033[44m
Magenta \033[35m \033[45m
Cyan \033[36m \033[46m
Light gray \033[37m \033[47m
Use default \033[39m \033[49m

Remember to restore the default color after the content you want colored.

As typing this is kind of cumbersome, you may want to add a bash alias.

Side note: if you have colored output and want to remove the color annotations, see this card

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Judith Roth
Last edit:
16 days ago
by Judith Roth
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