perl one-liner; 'randline' April 20, 2005

I have a directory on my hard drive which has a fair quantity of multimedia content. Occasionally, my listening choices (ok, I gave it away) get somewhat stale. Scrolling through a list of – well, quite a few choices can be somewhat daunting. I thought “hey! What if I chose entries at random for consideration! I’m sure there’s a what I can do that with some shell mumbo-jumbo.”

Turns out to be possible, but you need some sed fu, and why not use perl.

So now I can type

$ ls | randline

and get a random selection from the list. If I want to go all crazy and not even screen it, I can go with

$ xmms -e `ls | randline`.

Here’s the .bashrc entry I used:

    alias randline="perl -we 'srand ; rand(\$.) < 1 && (\$line = \$_) while <STDIN>; chomp(\$line); print \"\$line\\n\";'"

The ‘guts’ came from an entry in the Perl Cookbook, worth checking out due to their description of how it actually works. It’s a neat idea. Basically, you look at each line one by one. Each time you do you have a 1/(line number) chance of choosing that line as the one you’ll output. So if you just have one line, you’ve got a 11 chance of choosing that line. If you have 2, you start out with a taking the first line, and then having a 12 chance of picking the second – giving you 5050 odds you’ll have either the first or the second. It extends nicely.

Anyway, thanks to this, I’m currently listening to a cd I forgot I bought years ago which I’m really digging, fit my mood perfectly. The Blue Moods of Spain