Perl is supplied with extensive documentation. Enter perldoc perlre at a shell or DOS prompt to display the section covering Perl Regular Expressions. HTML versions are available at many locations including this version of Perl 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 "regex"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)$/. See similar questions...

Regexps just aren't powerful enough. Although Perl's patterns aren't strictly regular because they do backreferencing (the \1 notation), you still can't do it. You need to employ auxiliary logic. See similar questions...

You can test or manipulate strings using the built-in functions REGEXP_INSTR, REGEXP_REPLACE, and REGEXP_SUBSTR. Oracle's regular expression features use characters like '.', '*', '^', and '$' that you might be familiar with from UNIX or Perl programming. For multi-language programming, there are also extensions such as '[:lower:]' to match a lowercase letter, instead of '[a-z]' which does not match lowercase accented letters. See similar questions...

Yes. New in v1.1.5, DenyHosts adds the ability for the user to specify additional regular expressions that can be used to locate possible break-in attempts. The USERDEF_FAILED_ENTRY_REGEX can be specified repeatedly. Each value must contain a single regular expression that includes a host regular expression group and optionally a user group. It is assumed that the end user is familiar with regular expressions in order to take advantage of this feature. See similar questions...

The or operator is '\|', not '|', and the grouping operators are '\(' and '\)'. Also, the string syntax for a backslash is '\\'. To specify a regular expression like 'xxx\(foo\|bar\)' in a Lisp string, use 'xxx\\(foo\\|bar\\)'. Unlike in Unix grep, sed, etc., a complement character set ('[^...]') can match a newline character (<LFD> a.k.a. C-j a.k.a. '\n'), unless newline is mentioned as one of the characters not to match. The character syntax regexps (e.g. See similar questions...

No. Regular expressions were an option, but both the search time due to server overhead and the steep learning curve for the average user have made us decide to drop the idea. However, you will find that the equal sign option offers ample power and flexibility to your search. See similar questions...

What is the easiest way to execute a template, but write the output to a file, to be used as static HTML. The Tea Template Language document has a section titled "Java Integration". The SimpleTea example shows how to integrate with the Tea compiler and runtime. This example outputs to a String, but it can easily be adapted to write to files. See similar questions...

Very powerful addition to the Find command. I used: Caption=[A-Z]\w+ to find all lines with Caption followed by = and a Capital Letter, followed by any letters and a space. Then F3 gave me the next. Learn them! There is an explanation of how to use Regular Expressions here. See similar questions...

There are many regular expression engines. ORF uses PCRE engine (Perl-Compatible Regular Expressions), which implements (almost) the same syntax and semantics as Perl 5 (see http://www.pcre.org and http://www.pcre.org/pcre.txt [warning! large file] for documentation). Note that it is not the same engine used by Perl, Java or the .NET Framework. See similar questions...

With Mailfilter you can define your own filter rules to determine which e-mails are considered waste and what should be downloaded into your local computer. Such rules are defined by using Regular Expressions. It is very common for these kinds of programs to employ this technique because of its great flexibility. See similar questions...

NSP actually checks each regular expression one by one. Unfortunately if the list of regex's is very long, this becomes too slow computationally, and so instead we actually concatenate all the regular expressions to form one big regex, which is then used to do the matching. For example given the regexes above, they will be combined into a single regex, like so: and then this regex is used to do the matching. See similar questions...

Yes, you can use regular expressions to exclude or include certain types, methods, and fields. You can do this using the GUI by adding rule nodes in the rule editing view located on the right pane of the exclude or include tabs on any of the configuration editors. For example, if you want to create a regular expression that matches methods beginning with "Test"... Click the "Add Type" button. See similar questions...

Both Basic Regular Expressions (BREs) and Extended Regular Expressions (EREs) are supported and are described in XBD, Chapter 9, Regular Expressions and all of the utilities and interfaces that use regular expressions refer back to this definition. The functions regcomp() and regexec() in XSH, Chapter 3, System Interfaces implement regular expressions as defined in the Single UNIX Specification. See similar questions...

Generally speaking, the performance characteristics of any regular expression or simple search string are the same. The only exception is that regular expressions with capturing groups (the round brackets) can be much slower than those without, in the worst case. This is a challenging problem in theoretical computer science. Nevertheless, we've put considerable time and effort into optimising regex search performance capturing groups. See similar questions...

When using MATCHES or MATCHALL in an IF command, or using any of the STRING(REGEX ...) commands, CMake expects regular expressions, not globs (wild cards). CMake uses the same regular expression engine above all platforms. Here are the meanings of the metacharacters: ^ Matches at beginning of a line $ Matches at end of a line . See similar questions...

First read Question 4.16, '' What does it mean to put a regular expression within a BNF production?'' . For regular expressions that are simply strings, you might as well put them directly into the BNF productions, and not bother with defining them in a regular expression production.6 For more complex regular expressions, it is best to give them a name, using a regular expression production. There are two reasons for this. The first is error reporting. See similar questions...