Overview
--------

Hath is a Haskell program for working with network blocks in CIDR[1]
notation. When dealing with blocks of network addresses, there are a
few things that you (i.e. I) want to do with them:

  * Create a regular expression matching the CIDR block(s). This is
    because grep will throw up if you feed it CIDR.

  * Combine small blocks into larger ones. For example, if you have two
    consecutive /24s, they might combine into a larger /23.

  * View the result of block combination in a useful way.

Hath does just that. It takes as its input (via stdin, or a file with
the -i parameter) a list of CIDR blocks. From now on, assume we have
the following in cidrs.txt:

  10.0.0.0/24
  10.0.1.0/24


Modes
-----

Hath has the following modes:

  * Regexed

    This computes a (Perl-compatible) regular expression matching
    the input CIDR blocks. It's the default mode of operation.

      $ hath -i cidrs.txt
      ([^\.0-9](10)\.(0)\.(0)\.(0)[^\.0-9]|[^\.0-9](10)\.(0)\.(1)
      \.(0)[^\.0-9])

  * Reduced

    This combines small blocks into larger ones where possible, and
    eliminates redundant blocks. The output should be equivalent to
    the input, though.

      $ hath reduced -i cidrs.txt
      10.0.0.0/23

  * Duped

    Shows only the blocks that would be removed by reduce; that is, it
    shows the ones that would get combined into larger blocks or are
    simply redundant.

      $ hath duped -i cidrs.txt
      10.0.0.0/24
      10.0.1.0/24

  * Diffed

    Shows what would change if you used reduce. Uses diff-like
    notation.

      $ hath diffed -i cidrs.txt
      -10.0.0.0/24
      -10.0.1.0/24
      +10.0.0.0/23

Each of the modes also supports a present-tense flavor; the following
are equivalent to their counterparts: regex, reduce, dupe, diff.


Bugs
----

Send bugs to the moon[2].



[1] http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing

[2] michael@orlitzky.com