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From: merlyn@iwarp.intel.com (Randal L. Schwartz)
Newsgroups: comp.lang.perl
Subject: Re: path truncation quest
Keywords: path,truncation
Message-ID: <1991Mar21.174954.21421@iwarp.intel.com>
Date: 21 Mar 91 17:49:54 GMT
References: <1991Mar21.010547.13331@convex.com> <1991Mar21.064642.29427@eng.umd.edu>
Sender: news@iwarp.intel.com
Reply-To: merlyn@iwarp.intel.com (Randal L. Schwartz)
Organization: Stonehenge; netaccess via Intel, Beaverton, Oregon, USA
Lines: 47
In-Reply-To: ziegast@eng.umd.edu (Eric W. Ziegast)

In article <1991Mar21.064642.29427@eng.umd.edu>, ziegast@eng (Eric W. Ziegast) writes:
| In article <1991Mar21.010547.13331@convex.com> you write:
| >Any suggestions on how, given the argument "/directory/sub/100.host.0"
| >that one could take off the "100.host.0" component, leaving
| >"/directory/sub" ?
| 
| At first, I thought about using an array:
| 
| 	@tmp = split(/\//,$path);
| 	$dir = join("/",pop(@tmp));
| 
| But in Perl, there's always a better way of doing things:
| 
| 	$path =~ s/((\/[^\s\/]+)+)\/([^\s\/]+)/$1/;
| 
| A simplified version would be:
| 
| 	/((\/F)+)+)\/(F)/
| 
| 	F matches a one word file/directory name.
| 		In my example I use [^\s\/]+ which simply matches
| 		any word without whitespace or "/" in it.
| 		You may want to use something more strict instead.
| 
| 	$1 will match the directory path.  (man dirname)
| 	$2 is used only for /F grouping
| 	$3 will match the base name.  (man basename)
| 
| This is, of course, only if it's a full path name.  Anything else
| won't match (and won't be changed).

Ouch.  Why not just:

	$path =~ s#^(/.*)/.*$#$1#;

(If you have newlines in your filenames, replace "." with "(.|\n)".)

The nested "+" ops aren't buying you anything, nor is the paren-pair
on the right side.  And .* in the left is guaranteed to match the
longest string.

$_ = "/Just/another/Perl/hacker,/OK?"; s#^(/.*)/.*$#$1#; y#/# #; s/^.//; print
-- 
/=Randal L. Schwartz, Stonehenge Consulting Services (503)777-0095 ==========\
| on contract to Intel's iWarp project, Beaverton, Oregon, USA, Sol III      |
| merlyn@iwarp.intel.com ...!any-MX-mailer-like-uunet!iwarp.intel.com!merlyn |
\=Cute Quote: "Intel: putting the 'backward' in 'backward compatible'..."====/