michael orlitzky

Hath

Get It

The development version can be found in the hath git repository. There isn't an official release yet, because I haven't convinced myself that it's any good.

About

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 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.
1

2
```
$ 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.
1

2
```
$ 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.
1

2

3
```
$ 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.
1

2

3

4
```
$ 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

Email them to me at that address on the home page.