Dimsum is like head or tail, but pulls randomly from the entire file or stream

This doesn't come with an elaborate test suite, but it does pretty much everything that does in a few dozen lines of Perl.<p><a href="https://github.com/neilk/misc/blob/master/randline" rel="nofollow">https://github.com/neilk/misc/blob/master/randline</a><p>I've had this script (or versions of it) around for more than a decade. I didn't know the technique had a name.

uses reservoir sampling -<a href="http://en.wikipedia.org/wiki/Reservoir_sampling" rel="nofollow">http://en.wikipedia.org/wiki/Reservoir_sampling</a><p>(so it presumably consumes the entire stream before giving any results; any alternative i can think of would not be "really random" unless you knew the length of the stream in advance).

uhhh. You mean like shuf -n NNNN ?

I <i>really</i> don't like how this behaves for populating the array initially, and how it behaves for small inputs...<p><pre><code> $ seq 15 | dimsum -n 10 14 12 3 4 5 6 7 8 9 10</code></pre>