Colorize tail output

I wrote a script for this years ago. You can easily cover the case of multiple colors by piping successive invocations of highlight to each other.

From the README:

Usage: ./highlight [-i] [--color=COLOR_STRING] [--] <PATTERN0> [PATTERN1...]

This is highlight version 1.0.

This program takes text via standard input and outputs it with the given
perlre(1) pattern(s) highlighted with the given color.  If no color option
is specified, it defaults to 'bold red'.  Colors may be anything
that Perl's Term::ANSIColor understands.  This program is similar to
"grep --color PATTERN" except both matching and non-matching lines are
printed.

The default color can be selected via the $HIGHLIGHT_COLOR environment
variable.  The command-line option takes precedence.

Passing -i or --ignore-case will enable case-insensitive matching.

If your pattern begins with a dash ('-'), you can pass a '--' argument
after any options and before your pattern to distinguish it from an
option.

yes, there is way to do this. That is, as long as your terminal supports ANSI escape sequences. This is most terminals that exist.

I think I don't need explain how to grep, sed etc. point is the color right?

see below, this will make

WARN yellow
ERROR red
foo   green

here is example:

kent$ echo "WARN
ERROR
foo"|sed 's#WARN#\x1b[33m&#; s#ERROR#\x1b[31m&#; s#foo#\x1b[32m&#'

Note: \x1b is hexadecimal for the ESC character (^VEsc).

to see the result:

I wrote TxtStyle, a small utility for colorising logs. You define regular expressions to highlight in ~/.txts.conf file:

[Style="example"]
!red: regex("error")
green: regex("\d{4}-\d\d-\d\d")
# ...

And then apply the styles:

txts -n example example.log

or you can also pipe the output

tail -f example.log | txts -n example

I have been using a tool called grc for this for years. works like a charm. It comes with some quite good templates for many standard log outputs and formats and it is easy to define your own. A command I use often is

grc tail -f /var/log/syslog

It colorizes the syslog output so it is easy to spot errors (typically marked red.

Find the tool here:

https://github.com/garabik/grc

(it is also available as package for most common linux flavours).