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From: bob@its63b.ed.ac.uk (ERCF08 Bob Gray)
Newsgroups: net.unix
Subject: Re: Wildcard-specs
Message-ID: <77@its63b.ed.ac.uk>
Date: Thu, 9-Oct-86 12:46:12 EDT
Article-I.D.: its63b.77
Posted: Thu Oct  9 12:46:12 1986
Date-Received: Fri, 10-Oct-86 01:51:45 EDT
References: <4162@brl-smoke.ARPA>
Reply-To: bob@its63b.ed.ac.uk (Bob Gray)
Organization: I.T. School, Univ. of Edinburgh, U.K.
Lines: 57

In article <4162@brl-smoke.ARPA> lacasse@RAND-UNIX.arpa writes:
>
>If you have all day, you can use:
>    find . -exec grep string {} \;

You would be faster with
	grep string `find . -print`
provided that there weren't too many filenames. There is a
limit built into your system on the number of parameters you
can pass in an exec().

It has always seemed odd to me that a system with a
hierarchical file system didn't have some pattern which
recursively matched to sub directories and the files in
them. It would be very nice to do something like

	vi **.mk

to edit all the makefiles in a particular set of directories.

In most cases the pattern matching of
e.g.
	ls -l **
has the same meaning as
	ls -l `find . -print`

The problems begin when you attempt to make the "**"
wildcard as general as the other metacharacters. The pattern
"**x**"  means "find any file or directory which has the
letter x in its name. match to either the filename or
to ALL the files in the sub-tree if it is a directory.
i.e.
	**xyz**
should match to
	abcxyz.x
	abc/abcxyz.y
	abc/def/xxyzz/a.c
	abc/def/xxyzz/b.c
	abc/def/xxyzz/d.c
	abc/def/xxyzz/e.c

I started to implement "**" pattern matching in the Bourbe
shell a few years ago. Getting it to match with example 1.
was fairly trivial. The more general "**xyz**" case caused
an explosion in the number of filename matches before
sorting and elimination of duplicates. It was very easy to
run out of space on the machine I was working on in those days.

If I dig the code out of the archives, what sould happen in
a command like
	cp **.c x

where x is a directory. Should the shell quietly make new
directories or should it issue seperate cp commands for each
target directory, then let cp complain if they don't exist.
	Bob Gray.
	ERCC.