Hath is a Haskell program for working with network blocks in CIDR
notation. When dealing with blocks of network addresses, there are a
few things that one usually wants 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.
List them.
Hath has several modes to perform these functions:
Regexed
This computes a (Perl-compatible) regular expression matching
the input CIDR blocks. It's the default mode of operation.
Reduced
This combines small blocks into larger ones where possible, and
eliminates redundant blocks. The output should be equivalent to
the input, though.
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.
Diffed
Shows what would change if you used reduce. Uses diff-like
notation.
Listed
List the IP addresses contained within the given CIDRs.
Examples:
Compute a (Perl-compatible) regular expression matching
the input CIDR blocks. It's the default mode of operation.
$ echo "10.0.0.0/29 10.0.0.8/29" | hath
((10).(0).(0).(15|14|13|12|11|10|9|8|7|6|5|4|3|2|1|0))
Combine two /24s into a /23:
$ echo "10.0.0.0/24 10.0.1.0/24" | hath reduced
10.0.0.0/23
List the addresses in 192.168.0.240/29:
$ echo 192.168.0.240/29 | hath listed
192.168.0.240
192.168.0.241
192.168.0.242
192.168.0.243
192.168.0.244
192.168.0.245
192.168.0.246
192.168.0.247
The command-line syntax and complete set of options are documented in
the man page.
