Received: (qmail 95486 invoked by uid 501); 1 Nov 2000 07:28:15 -0000
Message-Id: <20001101072815.95485.qmail@locus.apache.org>
Date: 1 Nov 2000 07:28:15 -0000
From: era eriksson <era@suespammers.org>
Reply-To: era@suespammers.org
To: submit@bugz.apache.org
Subject: FAQ question B.9 contains a minor regex error in the example
X-Send-Pr-Version: 3.110

>Number:         6777
>Category:       documentation
>Synopsis:       FAQ question B.9 contains a minor regex error in the example
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    apache
>State:          closed
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          doc-bug
>Submitter-Id:   apache
>Arrival-Date:   Tue Oct 31 23:30:01 PST 2000
>Closed-Date:    Wed Nov 01 11:18:55 PST 2000
>Last-Modified:  Wed Nov 01 11:18:55 PST 2000
>Originator:     era@suespammers.org
>Release:        1.3.14
>Organization:
>Environment:
http://www.apache.org/docs/misc/FAQ.html
>Description:
<http://httpd.apache.org/docs/misc/FAQ.html#regex> presently reads:

 < What are "regular expressions"?
 < 
 < Regular expressions are a way of describing a pattern - for
 < example, "all the words that begin with the letter A" or "every
 < 10-digit phone number" or even "Every sentence with two commas in
 < it, and no capital letter Q". Regular expressions (aka "regexp"s)
 < are useful in Apache because they let you apply certain attributes
 < against collections of files or resources in very flexible ways -
 < for example, all .gif and .jpg files under any "images" directory
 < could be written as /.*\/images\/.*[jpg|gif]/.

The error here could not be described as "minor" but since it's just
an innocent example of what a regex looks like, it's not very critical.

As any grade school kid can tell you, the [] construct in regex-ese
defines a character class. Thus, the above example matches file names
under /images/ which contain any one of the characters f, g, i, j, p,
or | (having sorted the character list and elided duplicates).

The correct regex which corresponds to the prose description in the
answer is (jpg|gif) assuming you really do use Perl-compatible regular
expressions (too lazy to check -- I'm only just starting out with my
first Apache installation). Possibly you would actually also want to
remove the superfluous leading .* and anchor the search at the end,
and allow for "jpeg" as well as "jpg", yielding the regular expression
/\/images\/.*(jpe?g|gif)$/.

See also Jeffrey Friedl's _Mastering_Regular_Expressions_ (O'Reilly 1997)
<http://www.oreilly.com/catalog/regex/>

BTW, I'm with Friedl on the following terminology issue: "regexp" is
hard to handle in English, so perhaps you might prefer to use "regex".
>How-To-Repeat:

>Fix:

>Release-Note:
>Audit-Trail:
State-Changed-From-To: open-closed
State-Changed-By: slive
State-Changed-When: Wed Nov  1 11:18:52 PST 2000
State-Changed-Why:

Thanks.  This is now fixed.

Release-Changed-From-To: FAQ $Revision: 1.146 $ ($Date: 2000/09/12 02:29:10 $) -- http://www.apache.org/docs/misc/FAQ.html-1.3.14
Release-Changed-By: slive
Release-Changed-When: Wed Nov  1 11:18:52 PST 2000
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