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Comment by jlgreco | Hacker News Reader

You should do a screencast of such infinitely useful classics as tac, tsort, and sl.

(Actually, I have found use for those first two on occasion. ;)

Thanks for the suggestion! Actually, I initially wanted to do one on more advanced commands, but I thought I'd better lay a foundation first. I also want to cover using pipe (|) to chain these commands together. I'll make sure to include these.

Don't miss xargs.

tsort is one of my favorites, mostly because it's totally pointless until you need it and then it works exactly right. I love it.

Wow. I just read the man page for tsort and I am none the wiser.

  tsort takes a list of pairs of node names representing directed arcs in a 
  graph and prints the nodes in topologi-cal order on standard output.

It's not often I understand nothing on a man page. But this time, I'm stumped!

http://en.wikipedia.org/wiki/Topological_sorting

Say you have a set of tasks you need to do, and some of those depend on others. Now, you want to perform those tasks in order. The question then becomes: in which order? That's the problem that tsort (1) solves.

It's a way to do some of what make does without having to write a Makefile. 99.9% of the time, it never comes up, but when it does, it is very, very handy to be able to this in a shell pipeline. HTH.

Me too. Then I read the info, it gives an interesting historical perspective of why tsort came about. On a system with GNU utils installed:

  info coreutils 'tsort invocation'

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