<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="generator" content="rustdoc">
<meta name="description" content="API documentation for the Rust `Regex` struct in crate `regex`.">
<meta name="keywords" content="rust, rustlang, rust-lang, Regex">
<title>regex::Regex - Rust</title>
<link rel="stylesheet" type="text/css" href="../rustdoc.css">
<link rel="stylesheet" type="text/css" href="../main.css">
</head>
<body class="rustdoc">
<!--[if lte IE 8]>
<div class="warning">
This old browser is unsupported and will most likely display funky
things.
</div>
<![endif]-->
<nav class="sidebar">
<p class='location'><a href='index.html'>regex</a></p><script>window.sidebarCurrent = {name: 'Regex', ty: 'struct', relpath: ''};</script><script defer src="sidebar-items.js"></script>
</nav>
<nav class="sub">
<form class="search-form js-only">
<div class="search-container">
<input class="search-input" name="search"
autocomplete="off"
placeholder="Click or press ‘S’ to search, ‘?’ for more options…"
type="search">
</div>
</form>
</nav>
<section id='main' class="content struct">
<h1 class='fqn'><span class='in-band'>Struct <a href='index.html'>regex</a>::<wbr><a class='struct' href=''>Regex</a></span><span class='out-of-band'><span id='render-detail'>
<a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">
[<span class='inner'>−</span>]
</a>
</span><a class='srclink' href='../src/regex/re_unicode.rs.html#132' title='goto source code'>[src]</a></span></h1>
<pre class='rust struct'>pub struct Regex(_);</pre><div class='docblock'><p>A compiled regular expression for matching Unicode strings.</p>
<p>It is represented as either a sequence of bytecode instructions (dynamic)
or as a specialized Rust function (native). It can be used to search, split
or replace text. All searching is done with an implicit <code>.*?</code> at the
beginning and end of an expression. To force an expression to match the
whole string (or a prefix or a suffix), you must use an anchor like <code>^</code> or
<code>$</code> (or <code>\A</code> and <code>\z</code>).</p>
<p>While this crate will handle Unicode strings (whether in the regular
expression or in the search text), all positions returned are <strong>byte
indices</strong>. Every byte index is guaranteed to be at a Unicode code point
boundary.</p>
<p>The lifetimes <code>'r</code> and <code>'t</code> in this crate correspond to the lifetime of a
compiled regular expression and text to search, respectively.</p>
<p>The only methods that allocate new strings are the string replacement
methods. All other methods (searching and splitting) return borrowed
pointers into the string given.</p>
<h1 id='examples' class='section-header'><a href='#examples'>Examples</a></h1>
<p>Find the location of a US phone number:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>"[0-9]{3}-[0-9]{3}-[0-9]{4}"</span>).<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>mat</span> <span class='op'>=</span> <span class='ident'>re</span>.<span class='ident'>find</span>(<span class='string'>"phone: 111-222-3333"</span>).<span class='ident'>unwrap</span>();
<span class='macro'>assert_eq</span><span class='macro'>!</span>((<span class='ident'>mat</span>.<span class='ident'>start</span>(), <span class='ident'>mat</span>.<span class='ident'>end</span>()), (<span class='number'>7</span>, <span class='number'>19</span>));</pre>
<h1 id='using-the-stdstrpattern-methods-with-regex' class='section-header'><a href='#using-the-stdstrpattern-methods-with-regex'>Using the <code>std::str::pattern</code> methods with <code>Regex</code></a></h1>
<blockquote>
<p><strong>Note</strong>: This section requires that this crate is compiled with the
<code>pattern</code> Cargo feature enabled, which <strong>requires nightly Rust</strong>.</p>
</blockquote>
<p>Since <code>Regex</code> implements <code>Pattern</code>, you can use regexes with methods
defined on <code>&str</code>. For example, <code>is_match</code>, <code>find</code>, <code>find_iter</code>
and <code>split</code> can be replaced with <code>str::contains</code>, <code>str::find</code>,
<code>str::match_indices</code> and <code>str::split</code>.</p>
<p>Here are some examples:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r"\d+"</span>).<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>haystack</span> <span class='op'>=</span> <span class='string'>"a111b222c"</span>;
<span class='macro'>assert</span><span class='macro'>!</span>(<span class='ident'>haystack</span>.<span class='ident'>contains</span>(<span class='kw-2'>&</span><span class='ident'>re</span>));
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>haystack</span>.<span class='ident'>find</span>(<span class='kw-2'>&</span><span class='ident'>re</span>), <span class='prelude-val'>Some</span>(<span class='number'>1</span>));
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>haystack</span>.<span class='ident'>match_indices</span>(<span class='kw-2'>&</span><span class='ident'>re</span>).<span class='ident'>collect</span>::<span class='op'><</span><span class='ident'>Vec</span><span class='op'><</span>_<span class='op'>>></span>(),
<span class='macro'>vec</span><span class='macro'>!</span>[(<span class='number'>1</span>, <span class='number'>4</span>), (<span class='number'>5</span>, <span class='number'>8</span>)]);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>haystack</span>.<span class='ident'>split</span>(<span class='kw-2'>&</span><span class='ident'>re</span>).<span class='ident'>collect</span>::<span class='op'><</span><span class='ident'>Vec</span><span class='op'><</span>_<span class='op'>>></span>(), <span class='macro'>vec</span><span class='macro'>!</span>[<span class='string'>"a"</span>, <span class='string'>"b"</span>, <span class='string'>"c"</span>]);</pre>
</div><h2 id='methods'>Methods</h2><h3 class='impl'><span class='in-band'><code>impl <a class='struct' href='../regex/struct.Regex.html' title='regex::Regex'>Regex</a></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/regex/re_unicode.rs.html#179-618' title='goto source code'>[src]</a></span></h3>
<div class='docblock'><p>Core regular expression methods.</p>
</div><div class='impl-items'><h4 id='method.new' class='method'><span id='new.v' class='invisible'><code>fn <a href='#method.new' class='fnname'>new</a>(re: &<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -> <a class='enum' href='https://doc.rust-lang.org/nightly/core/result/enum.Result.html' title='core::result::Result'>Result</a><<a class='struct' href='../regex/struct.Regex.html' title='regex::Regex'>Regex</a>, <a class='enum' href='../regex/enum.Error.html' title='regex::Error'>Error</a>></code></span></h4>
<div class='docblock'><p>Compiles a regular expression. Once compiled, it can be used repeatedly
to search, split or replace text in a string.</p>
<p>If an invalid expression is given, then an error is returned.</p>
</div><h4 id='method.is_match' class='method'><span id='is_match.v' class='invisible'><code>fn <a href='#method.is_match' class='fnname'>is_match</a>(&self, text: &<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -> <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.bool.html'>bool</a></code></span></h4>
<div class='docblock'><p>Returns true if and only if the regex matches the string given.</p>
<p>It is recommended to use this method if all you need to do is test
a match, since the underlying matching engine may be able to do less
work.</p>
<h1 id='example' class='section-header'><a href='#example'>Example</a></h1>
<p>Test if some text contains at least one word with exactly 13
Unicode word characters:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>text</span> <span class='op'>=</span> <span class='string'>"I categorically deny having triskaidekaphobia."</span>;
<span class='macro'>assert</span><span class='macro'>!</span>(<span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r"\b\w{13}\b"</span>).<span class='ident'>unwrap</span>().<span class='ident'>is_match</span>(<span class='ident'>text</span>));</pre>
</div><h4 id='method.find' class='method'><span id='find.v' class='invisible'><code>fn <a href='#method.find' class='fnname'>find</a><'t>(&self, text: &'t <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -> <a class='enum' href='https://doc.rust-lang.org/nightly/core/option/enum.Option.html' title='core::option::Option'>Option</a><<a class='struct' href='../regex/struct.Match.html' title='regex::Match'>Match</a><'t>></code></span></h4>
<div class='docblock'><p>Returns the start and end byte range of the leftmost-first match in
<code>text</code>. If no match exists, then <code>None</code> is returned.</p>
<p>Note that this should only be used if you want to discover the position
of the match. Testing the existence of a match is faster if you use
<code>is_match</code>.</p>
<h1 id='example-1' class='section-header'><a href='#example-1'>Example</a></h1>
<p>Find the start and end location of the first word with exactly 13
Unicode word characters:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>text</span> <span class='op'>=</span> <span class='string'>"I categorically deny having triskaidekaphobia."</span>;
<span class='kw'>let</span> <span class='ident'>mat</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r"\b\w{13}\b"</span>).<span class='ident'>unwrap</span>().<span class='ident'>find</span>(<span class='ident'>text</span>).<span class='ident'>unwrap</span>();
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>mat</span>.<span class='ident'>start</span>(), <span class='number'>2</span>);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>mat</span>.<span class='ident'>end</span>(), <span class='number'>15</span>);</pre>
</div><h4 id='method.find_iter' class='method'><span id='find_iter.v' class='invisible'><code>fn <a href='#method.find_iter' class='fnname'>find_iter</a><'r, 't>(&'r self, text: &'t <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -> <a class='struct' href='../regex/struct.Matches.html' title='regex::Matches'>Matches</a><'r, 't></code></span></h4>
<div class='docblock'><p>Returns an iterator for each successive non-overlapping match in
<code>text</code>, returning the start and end byte indices with respect to
<code>text</code>.</p>
<h1 id='example-2' class='section-header'><a href='#example-2'>Example</a></h1>
<p>Find the start and end location of every word with exactly 13 Unicode
word characters:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>text</span> <span class='op'>=</span> <span class='string'>"Retroactively relinquishing remunerations is reprehensible."</span>;
<span class='kw'>for</span> <span class='ident'>mat</span> <span class='kw'>in</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r"\b\w{13}\b"</span>).<span class='ident'>unwrap</span>().<span class='ident'>find_iter</span>(<span class='ident'>text</span>) {
<span class='macro'>println</span><span class='macro'>!</span>(<span class='string'>"{:?}"</span>, <span class='ident'>mat</span>);
}</pre>
</div><h4 id='method.captures' class='method'><span id='captures.v' class='invisible'><code>fn <a href='#method.captures' class='fnname'>captures</a><'t>(&self, text: &'t <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -> <a class='enum' href='https://doc.rust-lang.org/nightly/core/option/enum.Option.html' title='core::option::Option'>Option</a><<a class='struct' href='../regex/struct.Captures.html' title='regex::Captures'>Captures</a><'t>></code></span></h4>
<div class='docblock'><p>Returns the capture groups corresponding to the leftmost-first
match in <code>text</code>. Capture group <code>0</code> always corresponds to the entire
match. If no match is found, then <code>None</code> is returned.</p>
<p>You should only use <code>captures</code> if you need access to the location of
capturing group matches. Otherwise, <code>find</code> is faster for discovering
the location of the overall match.</p>
<h1 id='examples-1' class='section-header'><a href='#examples-1'>Examples</a></h1>
<p>Say you have some text with movie names and their release years,
like "'Citizen Kane' (1941)". It'd be nice if we could search for text
looking like that, while also extracting the movie name and its release
year separately.</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r"'([^']+)'\s+\((\d{4})\)"</span>).<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>text</span> <span class='op'>=</span> <span class='string'>"Not my favorite movie: 'Citizen Kane' (1941)."</span>;
<span class='kw'>let</span> <span class='ident'>caps</span> <span class='op'>=</span> <span class='ident'>re</span>.<span class='ident'>captures</span>(<span class='ident'>text</span>).<span class='ident'>unwrap</span>();
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>caps</span>.<span class='ident'>get</span>(<span class='number'>1</span>).<span class='ident'>unwrap</span>().<span class='ident'>as_str</span>(), <span class='string'>"Citizen Kane"</span>);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>caps</span>.<span class='ident'>get</span>(<span class='number'>2</span>).<span class='ident'>unwrap</span>().<span class='ident'>as_str</span>(), <span class='string'>"1941"</span>);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>caps</span>.<span class='ident'>get</span>(<span class='number'>0</span>).<span class='ident'>unwrap</span>().<span class='ident'>as_str</span>(), <span class='string'>"'Citizen Kane' (1941)"</span>);
<span class='comment'>// You can also access the groups by index using the Index notation.</span>
<span class='comment'>// Note that this will panic on an invalid index.</span>
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='kw-2'>&</span><span class='ident'>caps</span>[<span class='number'>1</span>], <span class='string'>"Citizen Kane"</span>);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='kw-2'>&</span><span class='ident'>caps</span>[<span class='number'>2</span>], <span class='string'>"1941"</span>);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='kw-2'>&</span><span class='ident'>caps</span>[<span class='number'>0</span>], <span class='string'>"'Citizen Kane' (1941)"</span>);</pre>
<p>Note that the full match is at capture group <code>0</code>. Each subsequent
capture group is indexed by the order of its opening <code>(</code>.</p>
<p>We can make this example a bit clearer by using <em>named</em> capture groups:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r"'(?P<title>[^']+)'\s+\((?P<year>\d{4})\)"</span>)
.<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>text</span> <span class='op'>=</span> <span class='string'>"Not my favorite movie: 'Citizen Kane' (1941)."</span>;
<span class='kw'>let</span> <span class='ident'>caps</span> <span class='op'>=</span> <span class='ident'>re</span>.<span class='ident'>captures</span>(<span class='ident'>text</span>).<span class='ident'>unwrap</span>();
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='kw-2'>&</span><span class='ident'>caps</span>[<span class='string'>"title"</span>], <span class='string'>"Citizen Kane"</span>);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='kw-2'>&</span><span class='ident'>caps</span>[<span class='string'>"year"</span>], <span class='string'>"1941"</span>);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>caps</span>.<span class='ident'>get</span>(<span class='number'>0</span>).<span class='ident'>unwrap</span>().<span class='ident'>as_str</span>(), <span class='string'>"'Citizen Kane' (1941)"</span>);
<span class='comment'>// You can also access the groups by name using the Index notation.</span>
<span class='comment'>// Note that this will panic on an invalid group name.</span>
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='kw-2'>&</span><span class='ident'>caps</span>[<span class='string'>"title"</span>], <span class='string'>"Citizen Kane"</span>);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='kw-2'>&</span><span class='ident'>caps</span>[<span class='string'>"year"</span>], <span class='string'>"1941"</span>);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='kw-2'>&</span><span class='ident'>caps</span>[<span class='number'>0</span>], <span class='string'>"'Citizen Kane' (1941)"</span>);
</pre>
<p>Here we name the capture groups, which we can access with the <code>name</code>
method or the <code>Index</code> notation with a <code>&str</code>. Note that the named
capture groups are still accessible with <code>get</code> or the <code>Index</code> notation
with a <code>usize</code>.</p>
<p>The <code>0</code>th capture group is always unnamed, so it must always be
accessed with <code>at(0)</code> or <code>[0]</code>.</p>
</div><h4 id='method.captures_iter' class='method'><span id='captures_iter.v' class='invisible'><code>fn <a href='#method.captures_iter' class='fnname'>captures_iter</a><'r, 't>(&'r self, text: &'t <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -> <a class='struct' href='../regex/struct.CaptureMatches.html' title='regex::CaptureMatches'>CaptureMatches</a><'r, 't></code></span></h4>
<div class='docblock'><p>Returns an iterator over all the non-overlapping capture groups matched
in <code>text</code>. This is operationally the same as <code>find_iter</code>, except it
yields information about capturing group matches.</p>
<h1 id='example-3' class='section-header'><a href='#example-3'>Example</a></h1>
<p>We can use this to find all movie titles and their release years in
some text, where the movie is formatted like "'Title' (xxxx)":</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r"'(?P<title>[^']+)'\s+\((?P<year>\d{4})\)"</span>)
.<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>text</span> <span class='op'>=</span> <span class='string'>"'Citizen Kane' (1941), 'The Wizard of Oz' (1939), 'M' (1931)."</span>;
<span class='kw'>for</span> <span class='ident'>caps</span> <span class='kw'>in</span> <span class='ident'>re</span>.<span class='ident'>captures_iter</span>(<span class='ident'>text</span>) {
<span class='macro'>println</span><span class='macro'>!</span>(<span class='string'>"Movie: {:?}, Released: {:?}"</span>,
<span class='kw-2'>&</span><span class='ident'>caps</span>[<span class='string'>"title"</span>], <span class='kw-2'>&</span><span class='ident'>caps</span>[<span class='string'>"year"</span>]);
}
<span class='comment'>// Output:</span>
<span class='comment'>// Movie: Citizen Kane, Released: 1941</span>
<span class='comment'>// Movie: The Wizard of Oz, Released: 1939</span>
<span class='comment'>// Movie: M, Released: 1931</span></pre>
</div><h4 id='method.split' class='method'><span id='split.v' class='invisible'><code>fn <a href='#method.split' class='fnname'>split</a><'r, 't>(&'r self, text: &'t <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -> <a class='struct' href='../regex/struct.Split.html' title='regex::Split'>Split</a><'r, 't></code></span></h4>
<div class='docblock'><p>Returns an iterator of substrings of <code>text</code> delimited by a match of the
regular expression. Namely, each element of the iterator corresponds to
text that <em>isn't</em> matched by the regular expression.</p>
<p>This method will <em>not</em> copy the text given.</p>
<h1 id='example-4' class='section-header'><a href='#example-4'>Example</a></h1>
<p>To split a string delimited by arbitrary amounts of spaces or tabs:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r"[ \t]+"</span>).<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>fields</span>: <span class='ident'>Vec</span><span class='op'><</span><span class='kw-2'>&</span><span class='ident'>str</span><span class='op'>></span> <span class='op'>=</span> <span class='ident'>re</span>.<span class='ident'>split</span>(<span class='string'>"a b \t c\td e"</span>).<span class='ident'>collect</span>();
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>fields</span>, <span class='macro'>vec</span><span class='macro'>!</span>[<span class='string'>"a"</span>, <span class='string'>"b"</span>, <span class='string'>"c"</span>, <span class='string'>"d"</span>, <span class='string'>"e"</span>]);</pre>
</div><h4 id='method.splitn' class='method'><span id='splitn.v' class='invisible'><code>fn <a href='#method.splitn' class='fnname'>splitn</a><'r, 't>(&'r self, text: &'t <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>, limit: <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.usize.html'>usize</a>) -> <a class='struct' href='../regex/struct.SplitN.html' title='regex::SplitN'>SplitN</a><'r, 't></code></span></h4>
<div class='docblock'><p>Returns an iterator of at most <code>limit</code> substrings of <code>text</code> delimited
by a match of the regular expression. (A <code>limit</code> of <code>0</code> will return no
substrings.) Namely, each element of the iterator corresponds to text
that <em>isn't</em> matched by the regular expression. The remainder of the
string that is not split will be the last element in the iterator.</p>
<p>This method will <em>not</em> copy the text given.</p>
<h1 id='example-5' class='section-header'><a href='#example-5'>Example</a></h1>
<p>Get the first two words in some text:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r"\W+"</span>).<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>fields</span>: <span class='ident'>Vec</span><span class='op'><</span><span class='kw-2'>&</span><span class='ident'>str</span><span class='op'>></span> <span class='op'>=</span> <span class='ident'>re</span>.<span class='ident'>splitn</span>(<span class='string'>"Hey! How are you?"</span>, <span class='number'>3</span>).<span class='ident'>collect</span>();
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>fields</span>, <span class='macro'>vec</span><span class='macro'>!</span>(<span class='string'>"Hey"</span>, <span class='string'>"How"</span>, <span class='string'>"are you?"</span>));</pre>
</div><h4 id='method.replace' class='method'><span id='replace.v' class='invisible'><code>fn <a href='#method.replace' class='fnname'>replace</a><'t, R: <a class='trait' href='../regex/trait.Replacer.html' title='regex::Replacer'>Replacer</a>>(&self, text: &'t <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>, rep: R) -> <a class='enum' href='https://doc.rust-lang.org/nightly/collections/borrow/enum.Cow.html' title='collections::borrow::Cow'>Cow</a><'t, <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>></code></span></h4>
<div class='docblock'><p>Replaces the leftmost-first match with the replacement provided.
The replacement can be a regular string (where <code>$N</code> and <code>$name</code> are
expanded to match capture groups) or a function that takes the matches'
<code>Captures</code> and returns the replaced string.</p>
<p>If no match is found, then a copy of the string is returned unchanged.</p>
<h1 id='replacement-string-syntax' class='section-header'><a href='#replacement-string-syntax'>Replacement string syntax</a></h1>
<p>All instances of <code>$name</code> in the replacement text is replaced with the
corresponding capture group <code>name</code>.</p>
<p><code>name</code> may be an integer corresponding to the index of the
capture group (counted by order of opening parenthesis where <code>0</code> is the
entire match) or it can be a name (consisting of letters, digits or
underscores) corresponding to a named capture group.</p>
<p>If <code>name</code> isn't a valid capture group (whether the name doesn't exist
or isn't a valid index), then it is replaced with the empty string.</p>
<p>The longest possible name is used. e.g., <code>$1a</code> looks up the capture
group named <code>1a</code> and not the capture group at index <code>1</code>. To exert more
precise control over the name, use braces, e.g., <code>${1}a</code>.</p>
<p>To write a literal <code>$</code> use <code>$$</code>.</p>
<h1 id='examples-2' class='section-header'><a href='#examples-2'>Examples</a></h1>
<p>Note that this function is polymorphic with respect to the replacement.
In typical usage, this can just be a normal string:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>"[^01]+"</span>).<span class='ident'>unwrap</span>();
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>re</span>.<span class='ident'>replace</span>(<span class='string'>"1078910"</span>, <span class='string'>""</span>), <span class='string'>"1010"</span>);</pre>
<p>But anything satisfying the <code>Replacer</code> trait will work. For example,
a closure of type <code>|&Captures| -> String</code> provides direct access to the
captures corresponding to a match. This allows one to access
capturing group matches easily:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r"([^,\s]+),\s+(\S+)"</span>).<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>result</span> <span class='op'>=</span> <span class='ident'>re</span>.<span class='ident'>replace</span>(<span class='string'>"Springsteen, Bruce"</span>, <span class='op'>|</span><span class='ident'>caps</span>: <span class='kw-2'>&</span><span class='ident'>Captures</span><span class='op'>|</span> {
<span class='macro'>format</span><span class='macro'>!</span>(<span class='string'>"{} {}"</span>, <span class='kw-2'>&</span><span class='ident'>caps</span>[<span class='number'>2</span>], <span class='kw-2'>&</span><span class='ident'>caps</span>[<span class='number'>1</span>])
});
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>result</span>, <span class='string'>"Bruce Springsteen"</span>);</pre>
<p>But this is a bit cumbersome to use all the time. Instead, a simple
syntax is supported that expands <code>$name</code> into the corresponding capture
group. Here's the last example, but using this expansion technique
with named capture groups:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r"(?P<last>[^,\s]+),\s+(?P<first>\S+)"</span>).<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>result</span> <span class='op'>=</span> <span class='ident'>re</span>.<span class='ident'>replace</span>(<span class='string'>"Springsteen, Bruce"</span>, <span class='string'>"$first $last"</span>);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>result</span>, <span class='string'>"Bruce Springsteen"</span>);</pre>
<p>Note that using <code>$2</code> instead of <code>$first</code> or <code>$1</code> instead of <code>$last</code>
would produce the same result. To write a literal <code>$</code> use <code>$$</code>.</p>
<p>Sometimes the replacement string requires use of curly braces to
delineate a capture group replacement and surrounding literal text.
For example, if we wanted to join two words together with an
underscore:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r"(?P<first>\w+)\s+(?P<second>\w+)"</span>).<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>result</span> <span class='op'>=</span> <span class='ident'>re</span>.<span class='ident'>replace</span>(<span class='string'>"deep fried"</span>, <span class='string'>"${first}_$second"</span>);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>result</span>, <span class='string'>"deep_fried"</span>);</pre>
<p>Without the curly braces, the capture group name <code>first_</code> would be
used, and since it doesn't exist, it would be replaced with the empty
string.</p>
<p>Finally, sometimes you just want to replace a literal string with no
regard for capturing group expansion. This can be done by wrapping a
byte string with <code>NoExpand</code>:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>use</span> <span class='ident'>regex</span>::<span class='ident'>NoExpand</span>;
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r"(?P<last>[^,\s]+),\s+(\S+)"</span>).<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>result</span> <span class='op'>=</span> <span class='ident'>re</span>.<span class='ident'>replace</span>(<span class='string'>"Springsteen, Bruce"</span>, <span class='ident'>NoExpand</span>(<span class='string'>"$2 $last"</span>));
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>result</span>, <span class='string'>"$2 $last"</span>);</pre>
</div><h4 id='method.replace_all' class='method'><span id='replace_all.v' class='invisible'><code>fn <a href='#method.replace_all' class='fnname'>replace_all</a><'t, R: <a class='trait' href='../regex/trait.Replacer.html' title='regex::Replacer'>Replacer</a>>(&self, text: &'t <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>, rep: R) -> <a class='enum' href='https://doc.rust-lang.org/nightly/collections/borrow/enum.Cow.html' title='collections::borrow::Cow'>Cow</a><'t, <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>></code></span></h4>
<div class='docblock'><p>Replaces all non-overlapping matches in <code>text</code> with the replacement
provided. This is the same as calling <code>replacen</code> with <code>limit</code> set to
<code>0</code>.</p>
<p>See the documentation for <code>replace</code> for details on how to access
capturing group matches in the replacement string.</p>
</div><h4 id='method.replacen' class='method'><span id='replacen.v' class='invisible'><code>fn <a href='#method.replacen' class='fnname'>replacen</a><'t, R: <a class='trait' href='../regex/trait.Replacer.html' title='regex::Replacer'>Replacer</a>>(&self,<br> text: &'t <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>,<br> limit: <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.usize.html'>usize</a>,<br> rep: R)<br> -> <a class='enum' href='https://doc.rust-lang.org/nightly/collections/borrow/enum.Cow.html' title='collections::borrow::Cow'>Cow</a><'t, <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>></code></span></h4>
<div class='docblock'><p>Replaces at most <code>limit</code> non-overlapping matches in <code>text</code> with the
replacement provided. If <code>limit</code> is 0, then all non-overlapping matches
are replaced.</p>
<p>See the documentation for <code>replace</code> for details on how to access
capturing group matches in the replacement string.</p>
</div></div><h3 class='impl'><span class='in-band'><code>impl <a class='struct' href='../regex/struct.Regex.html' title='regex::Regex'>Regex</a></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/regex/re_unicode.rs.html#621-726' title='goto source code'>[src]</a></span></h3>
<div class='docblock'><p>Advanced or "lower level" search methods.</p>
</div><div class='impl-items'><h4 id='method.shortest_match' class='method'><span id='shortest_match.v' class='invisible'><code>fn <a href='#method.shortest_match' class='fnname'>shortest_match</a>(&self, text: &<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -> <a class='enum' href='https://doc.rust-lang.org/nightly/core/option/enum.Option.html' title='core::option::Option'>Option</a><<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.usize.html'>usize</a>></code></span></h4>
<div class='docblock'><p>Returns the end location of a match in the text given.</p>
<p>This method may have the same performance characteristics as
<code>is_match</code>, except it provides an end location for a match. In
particular, the location returned <em>may be shorter</em> than the proper end
of the leftmost-first match.</p>
<h1 id='example-6' class='section-header'><a href='#example-6'>Example</a></h1>
<p>Typically, <code>a+</code> would match the entire first sequence of <code>a</code> in some
text, but <code>shortest_match</code> can give up as soon as it sees the first
<code>a</code>.</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>text</span> <span class='op'>=</span> <span class='string'>"aaaaa"</span>;
<span class='kw'>let</span> <span class='ident'>pos</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r"a+"</span>).<span class='ident'>unwrap</span>().<span class='ident'>shortest_match</span>(<span class='ident'>text</span>);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>pos</span>, <span class='prelude-val'>Some</span>(<span class='number'>1</span>));</pre>
</div></div><h3 class='impl'><span class='in-band'><code>impl <a class='struct' href='../regex/struct.Regex.html' title='regex::Regex'>Regex</a></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/regex/re_unicode.rs.html#729-767' title='goto source code'>[src]</a></span></h3>
<div class='docblock'><p>Auxiliary methods.</p>
</div><div class='impl-items'><h4 id='method.as_str' class='method'><span id='as_str.v' class='invisible'><code>fn <a href='#method.as_str' class='fnname'>as_str</a>(&self) -> &<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a></code></span></h4>
<div class='docblock'><p>Returns the original string of this regex.</p>
</div><h4 id='method.capture_names' class='method'><span id='capture_names.v' class='invisible'><code>fn <a href='#method.capture_names' class='fnname'>capture_names</a>(&self) -> <a class='struct' href='../regex/struct.CaptureNames.html' title='regex::CaptureNames'>CaptureNames</a></code></span></h4>
<div class='docblock'><p>Returns an iterator over the capture names.</p>
</div><h4 id='method.captures_len' class='method'><span id='captures_len.v' class='invisible'><code>fn <a href='#method.captures_len' class='fnname'>captures_len</a>(&self) -> <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.usize.html'>usize</a></code></span></h4>
<div class='docblock'><p>Returns the number of captures.</p>
</div></div><h2 id='implementations'>Trait Implementations</h2><h3 class='impl'><span class='in-band'><code>impl <a class='trait' href='https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html' title='core::clone::Clone'>Clone</a> for <a class='struct' href='../regex/struct.Regex.html' title='regex::Regex'>Regex</a></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/regex/re_unicode.rs.html#131' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.clone' class='method'><span id='clone.v' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html#tymethod.clone' class='fnname'>clone</a>(&self) -> <a class='struct' href='../regex/struct.Regex.html' title='regex::Regex'>Regex</a></code></span></h4>
<div class='docblock'><p>Returns a copy of the value. <a href="https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html#tymethod.clone">Read more</a></p>
</div><h4 id='method.clone_from' class='method'><span id='clone_from.v' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html#method.clone_from' class='fnname'>clone_from</a>(&mut self, source: &Self)</code><div class='since' title='Stable since Rust version 1.0.0'>1.0.0</div></span></h4>
<div class='docblock'><p>Performs copy-assignment from <code>source</code>. <a href="https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html#method.clone_from">Read more</a></p>
</div></div><h3 class='impl'><span class='in-band'><code>impl <a class='trait' href='https://doc.rust-lang.org/nightly/core/fmt/trait.Display.html' title='core::fmt::Display'>Display</a> for <a class='struct' href='../regex/struct.Regex.html' title='regex::Regex'>Regex</a></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/regex/re_unicode.rs.html#148-153' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.fmt' class='method'><span id='fmt.v' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/fmt/trait.Display.html#tymethod.fmt' class='fnname'>fmt</a>(&self, f: &mut <a class='struct' href='https://doc.rust-lang.org/nightly/core/fmt/struct.Formatter.html' title='core::fmt::Formatter'>Formatter</a>) -> <a class='type' href='https://doc.rust-lang.org/nightly/core/fmt/type.Result.html' title='core::fmt::Result'>Result</a></code></span></h4>
<div class='docblock'><p>Shows the original regular expression.</p>
</div></div><h3 class='impl'><span class='in-band'><code>impl <a class='trait' href='https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html' title='core::fmt::Debug'>Debug</a> for <a class='struct' href='../regex/struct.Regex.html' title='regex::Regex'>Regex</a></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/regex/re_unicode.rs.html#155-160' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.fmt-1' class='method'><span id='fmt.v-1' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html#tymethod.fmt' class='fnname'>fmt</a>(&self, f: &mut <a class='struct' href='https://doc.rust-lang.org/nightly/core/fmt/struct.Formatter.html' title='core::fmt::Formatter'>Formatter</a>) -> <a class='type' href='https://doc.rust-lang.org/nightly/core/fmt/type.Result.html' title='core::fmt::Result'>Result</a></code></span></h4>
<div class='docblock'><p>Shows the original regular expression.</p>
</div></div><h3 class='impl'><span class='in-band'><code>impl <a class='trait' href='https://doc.rust-lang.org/nightly/core/str/trait.FromStr.html' title='core::str::FromStr'>FromStr</a> for <a class='struct' href='../regex/struct.Regex.html' title='regex::Regex'>Regex</a></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/regex/re_unicode.rs.html#169-176' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='associatedtype.Err' class='type'><span id='Err.t' class='invisible'><code>type <a href='https://doc.rust-lang.org/nightly/core/str/trait.FromStr.html#associatedtype.Err' class='type'>Err</a> = <a class='enum' href='../regex/enum.Error.html' title='regex::Error'>Error</a></code></span></h4>
<div class='docblock'><p>The associated error which can be returned from parsing.</p>
</div><h4 id='method.from_str' class='method'><span id='from_str.v' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/str/trait.FromStr.html#tymethod.from_str' class='fnname'>from_str</a>(s: &<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -> <a class='enum' href='https://doc.rust-lang.org/nightly/core/result/enum.Result.html' title='core::result::Result'>Result</a><<a class='struct' href='../regex/struct.Regex.html' title='regex::Regex'>Regex</a>, <a class='enum' href='../regex/enum.Error.html' title='regex::Error'>Error</a>></code></span></h4>
<div class='docblock'><p>Attempts to parse a string into a regular expression</p>
</div></div></section>
<section id='search' class="content hidden"></section>
<section class="footer"></section>
<aside id="help" class="hidden">
<div>
<h1 class="hidden">Help</h1>
<div class="shortcuts">
<h2>Keyboard Shortcuts</h2>
<dl>
<dt>?</dt>
<dd>Show this help dialog</dd>
<dt>S</dt>
<dd>Focus the search field</dd>
<dt>⇤</dt>
<dd>Move up in search results</dd>
<dt>⇥</dt>
<dd>Move down in search results</dd>
<dt>⏎</dt>
<dd>Go to active search result</dd>
<dt>+</dt>
<dd>Collapse/expand all sections</dd>
</dl>
</div>
<div class="infos">
<h2>Search Tricks</h2>
<p>
Prefix searches with a type followed by a colon (e.g.
<code>fn:</code>) to restrict the search to a given type.
</p>
<p>
Accepted types are: <code>fn</code>, <code>mod</code>,
<code>struct</code>, <code>enum</code>,
<code>trait</code>, <code>type</code>, <code>macro</code>,
and <code>const</code>.
</p>
<p>
Search functions by type signature (e.g.
<code>vec -> usize</code> or <code>* -> vec</code>)
</p>
</div>
</div>
</aside>
<script>
window.rootPath = "../";
window.currentCrate = "regex";
</script>
<script src="../jquery.js"></script>
<script src="../main.js"></script>
<script defer src="../search-index.js"></script>
</body>
</html>