What is clog?
=============

Clog is a filter that colorizes log files. Have you ever done something like
this:

    $ tail -f /var/log/something.log

Then left that running in a terminal, while you debug or run some program? Were
you able to spot important information as it scrolled by? Depending on the
volume of data scrolling by, it can be difficult to spot important information.

Clog is a filter, that you run like this:

    $ tail -f /var/log/something.log | clog something

The 'something' argument to clog is a section, which refers to a section in
~/.clogrc with a distinct set of rules. Those rules list patterns to look for,
and actions to take when the pattern is matched by a line. A typical example
might be that you want to highlight any line that contains the pattern 'severe'.
This entry in ~/clogrc achieves this:

    something rule /severe/ --> bold line

This rule is in the 'something' section, the pattern is 'severe', and the action
taken is to embolden the whole line. Pattern 'severe' should probably be more
restrictive, because it will also match words like 'persevered', but that is
optional.

Any color can be used, in both the 16- and 256-color space. Some examples are:

    bold
    underline
    bold blue
    underline on green
    black on white
    bold red on bright white
    rgb200 on grey4

Instead of coloring the whole line, specifying 'match' instead will only color
the parts of the line that match.

The format of the rules is:

    <section> rule /<pattern>/ --> <color> <action>

The section is simply a way to allow multiple rules sets, so that one .clogrc
file can serve multiple uses. The pattern is any supported Standard C Library
regular expression. Action must be one of 'line', 'match', 'suppress' or
'blank'.

Rules are processed in order, from top to bottom. This means that a rule defined
lower in the rc file gets to apply it's color later, and therefore 'on top of'
that of an earlier rule.

Note that there is a default section, called 'default'. Putting rules in the
default section means that you do not need to specify a section on the command
line. Multiple sections may be specified, and the rules are combined.

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