Bourne pipe operator parse ambiguity?

[thirdm]

I'm puzzled by this statement: "It is remarkable that in the four most recent editions of the UNIX system programmer’s manual the Bourne shell grammar described in the manual page does not admit the command who|wc. This is surely an oversight, but it suggests something darker: nobody really knows what the Bourne shell’s grammar is." -- http://doc.cat-v.org/plan_9/4th_edition/papers/rc

Reading the sh manual on NetBSD, the only other use of the pipe symbol I could find was in case statements to give multiple patterns in each alternative. I don't get what problem that could create. Does anyone know what Tom Duff is getting at?

[jggimi]

You might ask him -- his Email address is at the top of that page.

Looking at OpenBSD's sh(1) man page and the ksh(1) man page, which are slightly different ... I see a mention of who(1) as being one of the set of tracked aliases. wc(1) is not mentioned.

[unkmail]

I think he was talking about the very old systems. For ex. man sh from UNIX V3 http://minnie.tuhs.org/cgi-bin/utree.pl?file=V3 does not allow "|" as piplining command.