Path: utzoo!mnetor!uunet!husc6!mit-eddie!uw-beaver!cornell!batcomputer!pyramid!prls!mips!hansen
From: hansen@mips.UUCP (Craig Hansen)
Newsgroups: comp.unix.wizards
Subject: Re: csh oddity
Message-ID: <1326@mips.UUCP>
Date: 14 Jan 88 21:14:08 GMT
References: <826@murphy.UUCP> <590@devon.UUCP> <mips.1269> <1530@ogcvax.UUCP>
Lines: 59

In article <1530@ogcvax.UUCP>, schaefer@ogcvax.UUCP (Barton E. Schaefer) writes:
> In article <mips.1269> hansen@mips.UUCP (Craig Hansen) writes:
> >In article <826@murphy.UUCP> dcornutt@murphy.UUCP (Dave Cornutt) writes:
> >> I have discovered something peculiar about csh variable substitution.  Is
> >> this a bug or am I doing something wrong?
> >
> >You're doing something wrong. The correct syntax is:
> >
> >% set xy1z={$xy1z}_123
> 
> Sorry, Craig, that syntax changes the meaning of the {} from "variable
> substitution" to "filename substitution" as in
> 
> % set xy1z="one,two,three"
> % set xyz={$xy1z}_step
> % set
> xy1z	one,two,three
> xyz	(one_step two_step three_step)
> 
> The syntax ${xy1z} SHOULD work, but it doesn't (confirmed here for Mt. Xinu
> 4.3 BSD csh as well).  Does anyone happen to know why it fails?  Does it have
> anything to do with ${1} being a synonym for $1 (and ${2} for $2 and so on)?

OK, OK, it's a bug.

I haven't tested the fix, but the following fragment of source file sh.lex.c
looks dubious:

	default:
		if (digit(c)) {
/*
 * let $?0 pass for now
			if (special)
				goto vsyn;
*/
			while (digit(c = getC(DOEXCL))) {
				if (np < &name[sizeof name / 2])
					*np++ = c;
			}
		} else if (letter(c))
			while (letter(c = getC(DOEXCL))) {
				if (np < &name[sizeof name / 2])
					*np++ = c;
			}
		else
			goto vsyn;

Looks like the last call to letter() should be written as:

			while (letter(c = getC(DOEXCL)) || digit(c)) {

There's a macro called alnum(), which would be the obvious replacement,
but it evaluates the argument twice :-(.

-- 
Craig Hansen
Manager, Architecture Development
MIPS Computer Systems, Inc.
...{ames,decwrl,prls}!mips!hansen or hansen@mips.com