From mboxrd@z Thu Jan  1 00:00:00 1970
From: norman@nose.cs.utoronto.ca (Norman Wilson)
Date: Thu, 23 Jan 2003 22:09:51 -0500
Subject: [TUHS] The ^ = | ?
Message-ID: <pGdcVJPx3rqv.zrrJXl9y@192.168.0.10>

The earliest UNIX Programmer's Manual to describe shell
pipelines is the Third Edition, February 1973.  It gives a
syntax quite different from the modern one:

	com1 > com2 > com3 > outfile

meant what we would now write as

	com1 | com2 | com3 > outfile

This original syntax was pretty cumbersome; pretty
obviously it was put in as a quick hack (as were many
things in those early days).  Because > and < applied
only to the following word, pipelined commands with
arguments had to be quoted:

	who > "grep ken" >/tmp/kenlogins

Even worse, the shell had no inherent way to tell whether
the final word was a file or a program; if the last element
in a pipeline was to write to standard output, you had to
say so explicitly:

	who > "grep ken" >

On the other hand the syntax was symmetric: you could
also write

	"grep ken" < who <

pipe(II) also debuted in the Third Edition.

By the Fourth Edition (November 1973) there had evidently
been more time to think about the syntax; the modern notation
is shown, except that ^ is allowed as a synonym for |.  I have
long guessed that was because in those dark days of the
past, some upper-case-only terminals (remember stty lcase?)
offered no way to type | (and perhaps likewise {}`~) but I don't
really know.  Dennis?

Norman Wilson
Toronto ON