From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 7983 invoked from network); 30 Jul 2002 11:18:16 -0000 Received: from sunsite.dk (130.225.247.90) by ns1.primenet.com.au with SMTP; 30 Jul 2002 11:18:16 -0000 Received: (qmail 19 invoked by alias); 30 Jul 2002 11:17:52 -0000 Mailing-List: contact zsh-users-help@sunsite.dk; run by ezmlm Precedence: bulk X-No-Archive: yes X-Seq: 5194 Received: (qmail 7 invoked from network); 30 Jul 2002 11:17:51 -0000 To: zsh-users@sunsite.dk (Zsh users list) Subject: Re: POSIX compliance of shells - where to ask/talk about it? In-reply-to: "Ian Lynagh"'s message of "Thu, 25 Jul 2002 21:17:13 BST." <20020725201713.GA17071@stu163.keble.ox.ac.uk> Date: Tue, 30 Jul 2002 12:17:22 +0100 Message-ID: <10526.1028027842@csr.com> From: Peter Stephenson Sorry for the late reply... we've been implementing scatternets :-/ and it's been too hot to stay at home and stare at a computer at the weekend. (Yes, it's now raining again. Oh, and the power's just gone down, so everybody else has gone for lunch, so I might as well finish this...) Here is Your Handy Cut-Out-'N'-Keep Guide To Backslashing In Zsh. Ian Lynagh wrote: > Hi all, > > Where should one ask/talk about POSIX shell compliance (looking for a > mailing list probably)? You're probably not going to find anything better than one of the Open Group mailing lists, if you want the people that define the spec. The Austin Group is the one responsible for tinkering with Posix and other associated standards, including the shell specification. > printf "%s\n" `echo '\\\\\\\\\\\\\\\\'` > printf "%s\n" "`echo '\\\\\\\\\\\\\\\\'`" > > ... > > Using shells/zsh [invoked as sh]: > \\\\ > \\\\\\\\ There are various things going on here; in particular, both of the options BSD_ECHO and SH_GLOB are set for Bourne shell emulation. Here is standard zsh as a baseline: \\\\ \\\\ The number of backslashes has been halved twice, once by the original parsing of the backquoted expression, once by `echo' (not by the printf "%s", of course). The former happens because inside backquotes you can quote backquotes, so backslashes are active. Compare with: % printf "%s\n" $(echo '\\\\\\\\\\\\\\\\\') \\\\\\\\\ Since $(...) is terminated by a parenthesis, and the parenthesis is a standard terminator character in the shell (compare subshells with `(...)'), no backslash-stripping happens inside; the only layer of stripping is due to the echo. This distinction appears to be in bash, too. BSD_ECHO turns off the feature that the echo builtin (but not the print or printf builtins) interpret backslashes. This doubles the number you get back from the original commands: \\\\\\\\ \\\\\\\\ I think this is probably responsible for the other differences you saw, between bash and ash; it's certainly the difference between bash and the Solaris 8 system here's sh, since I've just tried echo '\\\\\\\\\\\\\\\\' on both and only sh halves the backquotes. This makes sense since the sh in this case is presumably of AT&T SYSV ancestry (the Solaris people can correct me if I'm wrong), hence doesn't have a BSD-like echo; /bin/echo is similar. The option SH_GLOB makes characters which are substituted by a parameter or command substitution elegible for further interpretation, providing the substitution was not quoted. In zsh, that means the number of \'s returned when the `...` is not quoted is halved, but inside double quotes it isn't. This gives what you observed, viz. \\\\ \\\\\\\\ This is definitely all a bit of a mess. I suspect the last feature can be regarded as a bug. The unfortunate fact that other shells think it's a good idea for text from parameter and command substitutions to be processed further as patterns etc. has given no end of trouble in zsh, and the SH_GLOB and SH_WORD_SPLIT options still don't emulate that behaviour (which, as far as I can tell, none of the current bunch of developers really like) properly. Maybe that :-/ should have been :-\. -- Peter Stephenson Software Engineer CSR Ltd., Science Park, Milton Road, Cambridge, CB4 0WH, UK Tel: +44 (0)1223 392070 ********************************************************************** The information transmitted is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. If you received this in error, please contact the sender and delete the material from any computer. **********************************************************************