March 2004

James Duncan Davidson has just released UnitKit version 0.6. A nice and simple unit testing framework with great Xcode integration!

Just found out the width-height ratio of any A0, A1, ..., An paper is 1:sqrt(2). Thus (if I'm not completely wrong) one should be able to use the function h(x) = sqrt(sqrt(2)) * (1 / sqrt(2))^x to get the height (in meters) of any paper of size Ax, and the function b(x) = h(x) / sqrt(2) (or b(x) = h(x + 1)) to get the width of any paper of size Ax. You never know when this might come in handy.

Suppose we have a list of IP addresses that we want sorted.

[prune:~] malte% cat iplist
1.2.3.4
1.121.3.222
1.21.3.4
1.121.3.5
1.121.3.4

Using sort we can specify that numeric comparison should take place and we end up with the following, sorted list.

[prune:~] malte% sort -n iplist
1.121.3.222
1.121.3.4
1.121.3.5
1.2.3.4
1.21.3.4

This isn't good enough as the numeric comparison is done only on the initial digit and the rest of the sort is performed lexically. For example 1.121.3.222 should come after both 1.121.3.4 and 1.121.3.5. The solution is to specify what fields to sort each line on. Using the -t switch we tell sort that fields are separated by dots. We then specify what fields to sort on using combined +n -m switches, where n and m are field indicies.

[prune:~] malte% sort -n -t '.' +0 -1 +1 -2 +2 -3 +3 -4 iplist
1.2.3.4
1.21.3.4
1.121.3.4
1.121.3.5
1.121.3.222

Voilà! A sorted list of IP addresses.