Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!cos!fetter
From: fetter@cos.com (Bob Fetter)
Newsgroups: comp.os.misc
Subject: Re: Globbing
Message-ID: <44431@cos.com>
Date: 30 Mar 91 01:33:40 GMT
References: <TB6AKE6@xds13.ferranti.com> <44381@cos.com> <ESAANQ5@xds13.ferranti.com>
Reply-To: fetter@cos.UUCP (Bob Fetter)
Organization: Corporation for Open Systems, McLean, VA
Lines: 106

In article <ESAANQ5@xds13.ferranti.com> peter@ficc.ferranti.com (Peter da Silva) writes:
>In article <44381@cos.com> fetter@cos.UUCP (Bob Fetter) writes:
>>   Um, with the small size and all, does that include support for
>> multiple commands and piping?  If so, it sounds like tight code!
>
>Nope. No backgrounding either.
>
>I like the quote nesting business, and the [glob *.c] stuff. I could
>make glob a builtin for efficiency, too.
>-- 
>Peter da Silva.  `-_-'  peter@ferranti.com
>+1 713 274 5180.  'U`  "Have you hugged your wolf today?"


  Well, one thing I've always liked from other systems is inline iteration.
This is a simple, yet powerful construct: one that seems both simpler
yet more powerful than equivalent looping/cycling constructs I've seen
in Unix shells.  (I'm sure there's powerful stuff out there... it's just
that I've not yet seen it all.)

  Iteration uses a list, this list contained within parenthesis.  For each
member of the list, the construct within which the list is embedded is
iterated upon and invoked.

  To take as an example, using the [..] syntax:

     touch ([glob *]).backup

will, once [glob *] is evaluated, say into: file1.c file1.o makefile readme

result in the execution of

     touch file1.c.backup
     touch file1.o.backup
     touch makefile.backup
     touch readme.backup

  Or, as another example, lets say wanting to put a single file in multiple
archives, all named with a '.archive' suffix:

     ar a ([glob *.archive]) the_file

  Of course, variable expansion should be supported:

     set MYLIST="fred joe bill wally"
     mail ($MYLIST) -f mailfile

		  <silly example, but used as an example).


  There are a few other rules on this form I've seen used, for
example, on Multics, where paired iteration lists would cycle in
tandem and where nesting of lists would be supported.

  But, I think I've presented the basic idea.  It would provide the
equivalent csh "foreach FOO () ... end" form as an instream syntatic
construct.  The examples I've given are quick, off-the-cuff.  More
powerful uses exist.

  One of the better uses of this form is to use 'globbing' against
commands which are constructed so as to only take *ONE* argument in a
particular syntatic position.  It repeats the command as required,
keeping the user happy and keeping the command from complaining.  Of
course, the list isn't limited to just 'globbing' expansion, but
could itself contain control arguments/flags or actual command names:
the use of a list of command names resulting in multiple commands
being run with identical argument lists.

=====

  OH, one example of paired lists *does* come to mind (quickly, he
said, before he submitted the article):

     diff ([glob *.c]) ([glob *.c.orig])

which, if we had a directory of .c files against which patch has been
run and we wanted to (for whatever reason) look at the results, would
do it for us.
  Lets say we had:
	file1.c
	file1.c.orig
	file2.c
	file2.c.orig
	file3.c
	file3.orig
	file4.c
	file4.c.orig

running the above diff command would, after [glob ..] processing, result
with:

	diff (file1.c file2.c file3.c file4.c) (file1.c.orig file2.c.orig file3.c.orig file4.c.orig)

which would cause the execution of:

	diff file1.c file1.c.orig
	diff file2.c file2.c.orig
	diff file3.c file3.c.orig
	diff file4.c file4.c.orig

=====

  Thoughts?  I hope this isn't too baroque, 'cause its really a
pleasure to use when its available.

  -Bob-