comm '! sort file1' '! sort file2'

[Guy Harris]

> Think of the havoc that results if I put a
> 	sort "$1" > ~/fifo & sort "$2" | comm - ~/fifo
> command into a shell script (named, for example, "scomm") and then,
> six months from now when I've forgotten the implementation details,
> type in
> 	scomm firstfile secondfile > results &
> 	scomm thirdfile fourthfile > moreresults &

At which point you say "Since the FIFO is a temporary file, I shouldn't just
save a FIFO in my home directory for a rainy day and use that; I should
create it at the beginning of the script, using "$$" in the name to make the
name unique, and delete it at the end!" and change the script to read like:

	fifoname=/tmp/scomm.$$
	trap "rm -f $fifoname; exit 1" 1 2 15
	/etc/mknod $fifoname p
	sort "$1" > $fifoname & sort "$2" | comm - $fifoname
	rm -f $fifoname
-- 
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy at sun.com (or guy at sun.arpa)