3.4. Setting Regular Expression Options

Problem

You want to compile a regular expression with all of the available matching modes: free-spacing, case insensitive, dot matches line breaks, and caret and dollar match at line breaks.

Solution

C#

Regex regexObj = new Regex("regex pattern",
    RegexOptions.IgnorePatternWhitespace | RegexOptions.IgnoreCase |
    RegexOptions.Singleline | RegexOptions.Multiline);

VB.NET

Dim RegexObj As New Regex("regex pattern",
    RegexOptions.IgnorePatternWhitespace Or RegexOptions.IgnoreCase Or
    RegexOptions.Singleline Or RegexOptions.Multiline)

Java

Pattern regex = Pattern.compile("regex pattern",
    Pattern.COMMENTS | Pattern.CASE_INSENSITIVE | Pattern.UNICODE_CASE |
    Pattern.DOTALL | Pattern.MULTILINE);

JavaScript

Literal regular expression in your code:

var myregexp = /regex pattern/im;

Regular expression retrieved from user input, as a string:

var myregexp = new RegExp(userinput, "im");

PHP

regexstring = '/regex pattern/simx';

Perl

m/regex pattern/simx;

Python

reobj = re.compile("regex pattern",
    re.VERBOSE | re.IGNORECASE |
    re.DOTALL | re.MULTILINE)

Ruby

Literal regular expression in your code:

myregexp = /regex pattern/mix;

Regular expression retrieved from user input, as a string:

myregexp = Regexp.new(userinput,
    Regexp::EXTENDED or Regexp::IGNORECASE or
    Regexp::MULTILINE);

Discussion

Many of the regular expressions in this book, and those that you find elsewhere, are written to be used with certain regex matching modes. There are four basic modes that nearly all modern regex flavors ...

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