> - CLIs are monodimensional, and suffer from the same problems that dataflow programming has: it's easy to split the flow of data into two pipes, but is really

> - CLIs are monodimensional, and suffer from the same problems that dataflow programming has: it's easy to split the flow of data into two pipes, but is really hard (semantically) to rejoin them. That's not hard if the text streams are line-oriented * append one to another, if order is not important * append one to another and then sort again, if order is important, * JOIN the streams using the `join' command (it's a standalone text utility, does pretty much what SQL JOIN does) To compute sum (in set theory sense), use ` | sort | uniq', to take intersection, use ` | sort | uniq -d'. Or use the `comm' utility. If using Bourne shell derivative, you may end up using temporary files. With the Rc shell, you may use the <{COMMAND} syntax, like: cat <{foo | bar | baz} <{frob | knob | bob} <{some | more} | subsequent | processing to catenate output of three pipes and do subsequent processing.