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<html><title>Programming Ruby: The Pragmatic Programmer's Guide</title><head><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><STYLE TYPE="text/css"><!--
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</STYLE><table bgcolor="#a03030" cellpadding="3" border="0" cellspacing="0"><tr><td colspan="3"><table bgcolor="#902020" cellpadding="20"><tr><td><h1 class="header">Programming Ruby</h1><h3 class="subheader">The Pragmatic Programmer's Guide</h3></td></tr></table></td></tr><tr><td width="33%" align="left"><a class="subheader" href="ref_c_range.html">Previous <</a></td><td width="33%" align="center" valign="middle"><a class="subheader" href="builtins.html">Contents ^</a><br></td><td width="33%" align="right"><a class="subheader" href="ref_c_string.html">Next ></a><br></td></tr></table></head><body bgcolor="white">
<!--
Copyright (c) 2001 by Addison Wesley Longman. This
material may be distributed only subject to the terms and
conditions set forth in the Open Publication License, v1.0 or
later (the latest version is presently available at
http://www.opencontent.org/openpub/).
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<table><tr><td height="20"><img src="dot.gif" width="1" height="20"></td></tr></table><table border="0" width="100%" bgcolor="660066" cellpadding="10"><tr><td valign="center"><font color="white" size="7">class Regexp</font></td><td><table border="0"><tr><td><font color="white">
Parent:
</font></td><td><font color="white">Object</font></td></tr><tr><td><font color="white">
Version:
</font></td><td><font color="white">
1.6
</font></td></tr></table></td></tr></table><p></p><H3>Index:</H3><a href="#compile">compile</a> <a href="#escape">escape</a> <a href="#last_match">last_match</a> <a href="#new">new</a> <a href="#quote">quote</a> <a href="#_eq_eq"><i>==</i></a> <a href="#_eq_eq_eq"><i>===</i></a> <a href="#_eq_sd"><i>=~</i></a> <a href="#_sd"><i>~</i></a> <a href="#casefold_qm"><i>casefold?</i></a> <a href="#kcode"><i>kcode</i></a> <a href="#match"><i>match</i></a> <a href="#source"><i>source</i></a> <p></p><hr>
A <code>Regexp</code> holds a regular expression, used to match a pattern against
strings. Regexps are created using the <code>/.../</code> and <code>%r{...}</code>
literals, and by the <a href="ref_c_regexp.html#new"><code>Regexp::new</code></a> constructor.
<P></P>
<table border="0" width="100%" cellpadding="10"><tr><td valign="center" colspan="3" bgcolor="990066"><font color="white" size="6">
constants
</font></td></tr></table><table border="2" cellpadding="5">
<tr>
<td valign="top"><tr>
<td><a name="EXTENDED"><code>EXTENDED</code></a></td>
<td></td>
<td>Ignore spaces and newlines in regexp.</td>
</tr>
<P></P>
<tr>
<td><a name="IGNORECASE"><code>IGNORECASE</code></a></td>
<td></td>
<td>Matches are case insensitive.</td>
</tr>
<P></P>
<tr>
<td><a name="MULTILINE"><code>MULTILINE</code></a></td>
<td></td>
<td>Newlines treated as any other character.</td>
</tr>
</td>
</tr>
</table><p></p>
<P></P>
<table border="0" width="100%" cellpadding="10"><tr><td valign="center" colspan="2" bgcolor="990066"><font color="white" size="6">class methods
</font></td></tr><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="compile"><b>compile</b></a></font></td><td bgcolor="#ffaaaa">
Regexp.compile( <i>pattern</i>
<i>[</i>, <i>options</i> <i>[</i><i>lang</i><i>]</i><i>]</i> )
-> <i>aRegexp</i>
</td></tr><td></td><td>
<P></P>
Synonym for <code>Regexp.new</code>.
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="escape"><b>escape</b></a></font></td><td bgcolor="#ffaaaa">
Regexp.escape( <i>aString</i> )
-> <i>aNewString</i>
</td></tr><td></td><td>
<P></P>
Escapes any characters that would have special meaning in a
regular expression. For any string,
<code>Regexp.escape(<i>str</i>)=~<i>str</i></code> will be true.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td valign="top"><code>Regexp.escape('\\*?{}.')</code></td>
<td valign="top"></td>
<td valign="top"><code>\\\\\*\?\{\}\.</code></td>
</tr>
</table>
<P></P>
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="last_match"><b>last_match</b></a></font></td><td bgcolor="#ffaaaa">
Regexp.last_match
-> <i>aMatchData</i>
</td></tr><td></td><td>
<P></P>
Returns the <code>MatchData</code> object generated by the last
successful pattern match. Equivalent to reading the global
variable <code>$~</code>. <code>MatchData</code> is described
on page 340.
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="new"><b>new</b></a></font></td><td bgcolor="#ffaaaa">
Regexp.new( <i>pattern</i>
<i>[</i>, <i>options</i> <i>[</i><i>lang</i><i>]</i><i>]</i> )
-> <i>aRegexp</i>
</td></tr><td></td><td>
<P></P>
Constructs a new regular expression from <i>pattern</i>, which can
be either a <code>String</code> or a <code>Regexp</code> (in which case that
regexp's options are not propagated). If <i>options</i> is
a <code>Fixnum</code>, it should be one or more of the constants
<code>Regexp::EXTENDED</code>, <code>Regexp::IGNORECASE</code>, and
<code>Regexp::POSIXLINE</code>, <em>or</em>-ed together.
Otherwise, if <i>options</i> is not
<code>nil</code>, the regexp will be case insensitive. The <i>lang</i>
parameter enables multibyte support for the regexp: `n', `N' = none,
`e', `E' = EUC, `s', `S' = SJIS, `u',
`U' = UTF-8.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td valign="top"><code>r1 = Regexp.new('^a-z+:\\s+\w+')</code></td>
<td valign="top"></td>
<td valign="top"><code>/^a-z+:\s+\w+/</code></td>
</tr>
<tr>
<td valign="top"><code>r2 = Regexp.new(r1, true)</code></td>
<td valign="top"></td>
<td valign="top"><code>/^a-z+:\s+\w+/i</code></td>
</tr>
<tr>
<td valign="top"><code>r3 = Regexp.new(r2, Regexp::EXTENDED)</code></td>
<td valign="top"></td>
<td valign="top"><code>/^a-z+:\s+\w+/x</code></td>
</tr>
</table>
<P></P>
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="quote"><b>quote</b></a></font></td><td bgcolor="#ffaaaa">
Regexp.quote( <i>aString</i> )
-> <i>aNewString</i>
</td></tr><td></td><td>
<P></P>
Synonym for <code>Regexp.escape</code>.
<P></P>
</td></table>
<P></P>
<table border="0" width="100%" cellpadding="10"><tr><td valign="center" colspan="2" bgcolor="990066"><font color="white" size="6">instance methods
</font></td></tr><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="_eq_eq"><b>==</b></a></font></td><td bgcolor="#ffaaaa">
<i>rxp</i> == <i>aRegexp</i>
-> <code>true</code> or <code>false</code>
</td></tr><td></td><td>
<P></P>
Equality---Two regexps are equal if their patterns are identical, they have
the same character set code, and their <code>casefold?</code> values are
the same.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td valign="top"><code>/abc/ == /abc/x</code></td>
<td valign="top"></td>
<td valign="top"><code>true</code></td>
</tr>
<tr>
<td valign="top"><code>/abc/ == /abc/i</code></td>
<td valign="top"></td>
<td valign="top"><code>false</code></td>
</tr>
<tr>
<td valign="top"><code>/abc/u == /abc/n</code></td>
<td valign="top"></td>
<td valign="top"><code>false</code></td>
</tr>
</table>
<P></P>
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="_eq_eq_eq"><b>===</b></a></font></td><td bgcolor="#ffaaaa">
<i>rxp</i> === <i>aString</i> -> <code>true</code> or <code>false</code>
</td></tr><td></td><td>
<P></P>
Case Equality---Synonym for <a href="ref_c_regexp.html#_eq_sd"><code>Regexp#=~</code></a> used in case statements.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
a = "HELLO"
case a
when /^a-z*$/; print "Lower case\n"
when /^A-Z*$/; print "Upper case\n"
else; print "Mixed case\n"
end
</pre></td></tr></table>
<em>produces:</em>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
Upper case
</pre></td></tr></table>
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="_eq_sd"><b>=~</b></a></font></td><td bgcolor="#ffaaaa">
<i>rxp</i> =~ <i>aString</i>
-> <i>anInteger</i> or <code>nil</code>
</td></tr><td></td><td>
<P></P>
Match---Matches <i>rxp</i> against <i>aString</i>, returning the offset
of the start of the match or <code>nil</code> if the match failed.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td valign="top"><code>/SIT/ =~ "insensitive"</code></td>
<td valign="top"></td>
<td valign="top"><code>nil</code></td>
</tr>
<tr>
<td valign="top"><code>/SIT/i =~ "insensitive"</code></td>
<td valign="top"></td>
<td valign="top"><code>5</code></td>
</tr>
</table>
<P></P>
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="_sd"><b>~</b></a></font></td><td bgcolor="#ffaaaa">
~ <i>rxp</i>
-> <i>anInteger</i> or <code>nil</code>
</td></tr><td></td><td>
<P></P>
Match---Matches <i>rxp</i> against the contents of <code>$_</code>. Equivalent to
<code><i>rxp</i> =~ $_</code>.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>$_ = "input data"</code></td>
</tr>
<tr>
<td valign="top"><code>~ /at/</code></td>
<td valign="top"></td>
<td valign="top"><code>7</code></td>
</tr>
</table>
<P></P>
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="casefold_qm"><b>casefold?</b></a></font></td><td bgcolor="#ffaaaa">
<i>rxp</i>.casefold? -> <code>true</code> or <code>false</code>
</td></tr><td></td><td>
<P></P>
Returns the value of the case-insensitive flag.
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="kcode"><b>kcode</b></a></font></td><td bgcolor="#ffaaaa">
<i>rxp</i>.kcode -> <i>aString</i>
</td></tr><td></td><td>
<P></P>
Returns the character set code for the regexp.
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="match"><b>match</b></a></font></td><td bgcolor="#ffaaaa">
<i>rxp</i>.match(<i>aString</i>)
-> <i>aMatchData</i> or <code>nil</code>
</td></tr><td></td><td>
<P></P>
Returns a <code>MatchData</code> object (see page 340)
describing the match, or <code>nil</code> if there was no match. This
is equivalent to retrieving the value of the special variable
<code>$~</code> following a normal match.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td valign="top"><code>/(.)(.)(.)/.match("abc")[2]</code></td>
<td valign="top"></td>
<td valign="top"><code>"b"</code></td>
</tr>
</table>
<P></P>
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="source"><b>source</b></a></font></td><td bgcolor="#ffaaaa">
<i>rxp</i>.source -> <i>aString</i>
</td></tr><td></td><td>
<P></P>
Returns the original string of the pattern.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td valign="top"><code>/ab+c/ix.source</code></td>
<td valign="top"></td>
<td valign="top"><code>"ab+c"</code></td>
</tr>
</table>
<P></P>
<P></P>
</td></table>
<P></P>
<p></p><hr><table bgcolor="#a03030" cellpadding="10" border="0" cellspacing="0"><tr><td width="33%" align="left"><a class="subheader" href="ref_c_range.html">Previous <</a></td><td width="33%" align="center" valign="middle"><a class="subheader" href="builtins.html">Contents ^</a><br></td><td width="33%" align="right"><a class="subheader" href="ref_c_string.html">Next ></a><br></td></tr></table><p></p><font size="-1">Extracted from the book "Programming Ruby -
The Pragmatic Programmer's Guide"</font><br><font size="-3">
Copyright
©
2000 Addison Wesley Longman, Inc. Released under the terms of the
<a href="http://www.opencontent.org/openpub/">Open Publication License</a> V1.0.
<br>
This reference is available for
<a href="http://www.pragmaticprogrammer.com/ruby/downloads/book.html">download</a>.
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