[TUHS] re: The ^ = | ?

Dennis Ritchie dmr at plan9.bell-labs.com
Fri Jan 24 17:22:12 AEST 2003

As Norman said, the earliest notation for
pipes used an extension (or abuse) of the semantics
of > and < .

Warren's memory of what Salus wrote (it's on p. 52-53)
is correct about the introduction of | (though I suspect
that McIlroy (whom Salus quotes) is being kind to me
when he said "he [Ken] couldn't bear to reveal my [Doug's]
ugly syntax."  Actually, I was responsible for the
particular < and > syntax as implemented, although the
whole idea came from much earlier on blackboard-only
ideas, and the blackboard was Doug's.

As to the original question: probably the ^ as an alternative
to | (which does seem to be there from the start, i.e. 4th
Edition) did have to do with character-set convenience
on upper-case-only terminals.  The TTY driver accepted
\! as an escape for |, but this was somewhat of a pain.


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