greg/mentat
1
0
Fork 0
Code Issues 294 Pull requests Projects Releases 9 Packages Wiki Activity
mentat/docs/apis/rust/regex/index.html

688 lines
43 KiB
HTML
Raw Normal View History

Add docs to documentation site
2018-06-21 14:44:35 +00:00
<!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` crate.">
<meta name="keywords" content="rust, rustlang, rust-lang, regex">
<title>regex - Rust</title>
<link rel="stylesheet" type="text/css" href="../normalize.css">
<link rel="stylesheet" type="text/css" href="../rustdoc.css"
id="mainThemeStyle">
<link rel="stylesheet" type="text/css" href="../dark.css">
<link rel="stylesheet" type="text/css" href="../light.css" id="themeStyle">
<script src="../storage.js"></script>
</head>
<body class="rustdoc mod">
<!--[if lte IE 8]>
<div class="warning">
This old browser is unsupported and will most likely display funky
things.
</div>
<![endif]-->
<nav class="sidebar">
<div class="sidebar-menu">&#9776;</div>
<p class='location'>Crate regex</p><div class="sidebar-elems"><div class="block items"><ul><li><a href="#modules">Modules</a></li><li><a href="#structs">Structs</a></li><li><a href="#enums">Enums</a></li><li><a href="#traits">Traits</a></li><li><a href="#functions">Functions</a></li></ul></div><p class='location'></p><script>window.sidebarCurrent = {name: 'regex', ty: 'mod', relpath: '../'};</script></div>
</nav>
<div class="theme-picker">
<button id="theme-picker" aria-label="Pick another theme!">
<img src="../brush.svg" width="18" alt="Pick another theme!">
</button>
<div id="theme-choices"></div>
</div>
<script src="../theme.js"></script>
<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"><h1 class='fqn'><span class='in-band'>Crate <a class="mod" 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'>&#x2212;</span>]
</a>
</span><a class='srclink' href='../src/regex/lib.rs.html#11-684' title='goto source code'>[src]</a></span></h1><div class='docblock'><p>This crate provides a library for parsing, compiling, and executing regular
expressions. Its syntax is similar to Perl-style regular expressions, but lacks
a few features like look around and backreferences. In exchange, all searches
execute in linear time with respect to the size of the regular expression and
search text.</p>
<p>This crate's documentation provides some simple examples, describes
<a href="#unicode">Unicode support</a> and exhaustively lists the
<a href="#syntax">supported syntax</a>.</p>
<p>For more specific details on the API for regular expressions, please see the
documentation for the <a href="struct.Regex.html"><code>Regex</code></a> type.</p>
<h1 id="usage" class="section-header"><a href="#usage">Usage</a></h1>
<p>This crate is <a href="https://crates.io/crates/regex">on crates.io</a> and can be
used by adding <code>regex</code> to your dependencies in your project's <code>Cargo.toml</code>.</p>
<pre><code class="language-toml">[dependencies]
regex = &quot;1&quot;
</code></pre>
<p>and this to your crate root:</p>
<pre class="rust rust-example-rendered">
<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">regex</span>;</pre>
<h1 id="example-find-a-date" class="section-header"><a href="#example-find-a-date">Example: find a date</a></h1>
<p>General use of regular expressions in this package involves compiling an
expression and then using it to search, split or replace text. For example,
to confirm that some text resembles a date:</p>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">regex</span>::<span class="ident">Regex</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&quot;^\d{4}-\d{2}-\d{2}$&quot;</span>).<span class="ident">unwrap</span>();
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">re</span>.<span class="ident">is_match</span>(<span class="string">&quot;2014-01-01&quot;</span>));</pre>
<p>Notice the use of the <code>^</code> and <code>$</code> anchors. In this crate, every expression
is executed with an implicit <code>.*?</code> at the beginning and end, which allows
it to match anywhere in the text. Anchors can be used to ensure that the
full text matches an expression.</p>
<p>This example also demonstrates the utility of
<a href="https://doc.rust-lang.org/stable/reference/tokens.html#raw-string-literals">raw strings</a>
in Rust, which
are just like regular strings except they are prefixed with an <code>r</code> and do
not process any escape sequences. For example, <code>&quot;\\d&quot;</code> is the same
expression as <code>r&quot;\d&quot;</code>.</p>
<h1 id="example-avoid-compiling-the-same-regex-in-a-loop" class="section-header"><a href="#example-avoid-compiling-the-same-regex-in-a-loop">Example: Avoid compiling the same regex in a loop</a></h1>
<p>It is an anti-pattern to compile the same regular expression in a loop
since compilation is typically expensive. (It takes anywhere from a few
microseconds to a few <strong>milliseconds</strong> depending on the size of the
regex.) Not only is compilation itself expensive, but this also prevents
optimizations that reuse allocations internally to the matching engines.</p>
<p>In Rust, it can sometimes be a pain to pass regular expressions around if
they're used from inside a helper function. Instead, we recommend using the
<a href="https://crates.io/crates/lazy_static"><code>lazy_static</code></a> crate to ensure that
regular expressions are compiled exactly once.</p>
<p>For example:</p>
<pre class="rust rust-example-rendered">
<span class="attribute">#[<span class="ident">macro_use</span>]</span> <span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">lazy_static</span>;
<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">regex</span>;
<span class="kw">use</span> <span class="ident">regex</span>::<span class="ident">Regex</span>;
<span class="kw">fn</span> <span class="ident">some_helper_function</span>(<span class="ident">text</span>: <span class="kw-2">&amp;</span><span class="ident">str</span>) <span class="op">-&gt;</span> <span class="ident">bool</span> {
<span class="macro">lazy_static</span><span class="macro">!</span> {
<span class="kw">static</span> <span class="kw-2">ref</span> <span class="ident">RE</span>: <span class="ident">Regex</span> <span class="op">=</span> <span class="ident">Regex</span>::<span class="ident">new</span>(<span class="string">&quot;...&quot;</span>).<span class="ident">unwrap</span>();
}
<span class="ident">RE</span>.<span class="ident">is_match</span>(<span class="ident">text</span>)
}
<span class="kw">fn</span> <span class="ident">main</span>() {}</pre>
<p>Specifically, in this example, the regex will be compiled when it is used for
the first time. On subsequent uses, it will reuse the previous compilation.</p>
<h1 id="example-iterating-over-capture-groups" class="section-header"><a href="#example-iterating-over-capture-groups">Example: iterating over capture groups</a></h1>
<p>This crate provides convenient iterators for matching an expression
repeatedly against a search string to find successive non-overlapping
matches. For example, to find all dates in a string and be able to access
them by their component pieces:</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&quot;(\d{4})-(\d{2})-(\d{2})&quot;</span>).<span class="ident">unwrap</span>();
<span class="kw">let</span> <span class="ident">text</span> <span class="op">=</span> <span class="string">&quot;2012-03-14, 2013-01-01 and 2014-07-05&quot;</span>;
<span class="kw">for</span> <span class="ident">cap</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">&quot;Month: {} Day: {} Year: {}&quot;</span>, <span class="kw-2">&amp;</span><span class="ident">cap</span>[<span class="number">2</span>], <span class="kw-2">&amp;</span><span class="ident">cap</span>[<span class="number">3</span>], <span class="kw-2">&amp;</span><span class="ident">cap</span>[<span class="number">1</span>]);
}
<span class="comment">// Output:</span>
<span class="comment">// Month: 03 Day: 14 Year: 2012</span>
<span class="comment">// Month: 01 Day: 01 Year: 2013</span>
<span class="comment">// Month: 07 Day: 05 Year: 2014</span></pre>
<p>Notice that the year is in the capture group indexed at <code>1</code>. This is
because the <em>entire match</em> is stored in the capture group at index <code>0</code>.</p>
<h1 id="example-replacement-with-named-capture-groups" class="section-header"><a href="#example-replacement-with-named-capture-groups">Example: replacement with named capture groups</a></h1>
<p>Building on the previous example, perhaps we'd like to rearrange the date
formats. This can be done with text replacement. But to make the code
clearer, we can <em>name</em> our capture groups and use those names as variables
in our replacement 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&quot;(?P&lt;y&gt;\d{4})-(?P&lt;m&gt;\d{2})-(?P&lt;d&gt;\d{2})&quot;</span>).<span class="ident">unwrap</span>();
<span class="kw">let</span> <span class="ident">before</span> <span class="op">=</span> <span class="string">&quot;2012-03-14, 2013-01-01 and 2014-07-05&quot;</span>;
<span class="kw">let</span> <span class="ident">after</span> <span class="op">=</span> <span class="ident">re</span>.<span class="ident">replace_all</span>(<span class="ident">before</span>, <span class="string">&quot;$m/$d/$y&quot;</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">after</span>, <span class="string">&quot;03/14/2012, 01/01/2013 and 07/05/2014&quot;</span>);</pre>
<p>The <code>replace</code> methods are actually polymorphic in the replacement, which
provides more flexibility than is seen here. (See the documentation for
<code>Regex::replace</code> for more details.)</p>
<p>Note that if your regex gets complicated, you can use the <code>x</code> flag to
enable insigificant whitespace mode, which also lets you write comments:</p>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">re</span> <span class="op">=</span> <span class="ident">Regex</span>::<span class="ident">new</span>(<span class="string">r&quot;(?x)
(?P&lt;y&gt;\d{4}) # the year
-
(?P&lt;m&gt;\d{2}) # the month
-
(?P&lt;d&gt;\d{2}) # the day
&quot;</span>).<span class="ident">unwrap</span>();
<span class="kw">let</span> <span class="ident">before</span> <span class="op">=</span> <span class="string">&quot;2012-03-14, 2013-01-01 and 2014-07-05&quot;</span>;
<span class="kw">let</span> <span class="ident">after</span> <span class="op">=</span> <span class="ident">re</span>.<span class="ident">replace_all</span>(<span class="ident">before</span>, <span class="string">&quot;$m/$d/$y&quot;</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">after</span>, <span class="string">&quot;03/14/2012, 01/01/2013 and 07/05/2014&quot;</span>);</pre>
<p>If you wish to match against whitespace in this mode, you can still use <code>\s</code>,
<code>\n</code>, <code>\t</code>, etc. For escaping a single space character, you can use its hex
character code <code>\x20</code> or temporarily disable the <code>x</code> flag, e.g., <code>(?-x: )</code>.</p>
<h1 id="example-match-multiple-regular-expressions-simultaneously" class="section-header"><a href="#example-match-multiple-regular-expressions-simultaneously">Example: match multiple regular expressions simultaneously</a></h1>
<p>This demonstrates how to use a <code>RegexSet</code> to match multiple (possibly
overlapping) regular expressions in a single scan of the search text:</p>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">regex</span>::<span class="ident">RegexSet</span>;
<span class="kw">let</span> <span class="ident">set</span> <span class="op">=</span> <span class="ident">RegexSet</span>::<span class="ident">new</span>(<span class="kw-2">&amp;</span>[
<span class="string">r&quot;\w+&quot;</span>,
<span class="string">r&quot;\d+&quot;</span>,
<span class="string">r&quot;\pL+&quot;</span>,
<span class="string">r&quot;foo&quot;</span>,
<span class="string">r&quot;bar&quot;</span>,
<span class="string">r&quot;barfoo&quot;</span>,
<span class="string">r&quot;foobar&quot;</span>,
]).<span class="ident">unwrap</span>();
<span class="comment">// Iterate over and collect all of the matches.</span>
<span class="kw">let</span> <span class="ident">matches</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="kw">_</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">set</span>.<span class="ident">matches</span>(<span class="string">&quot;foobar&quot;</span>).<span class="ident">into_iter</span>().<span class="ident">collect</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">matches</span>, <span class="macro">vec</span><span class="macro">!</span>[<span class="number">0</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">6</span>]);
<span class="comment">// You can also test whether a particular regex matched:</span>
<span class="kw">let</span> <span class="ident">matches</span> <span class="op">=</span> <span class="ident">set</span>.<span class="ident">matches</span>(<span class="string">&quot;foobar&quot;</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="op">!</span><span class="ident">matches</span>.<span class="ident">matched</span>(<span class="number">5</span>));
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">matches</span>.<span class="ident">matched</span>(<span class="number">6</span>));</pre>
<h1 id="pay-for-what-you-use" class="section-header"><a href="#pay-for-what-you-use">Pay for what you use</a></h1>
<p>With respect to searching text with a regular expression, there are three
questions that can be asked:</p>
<ol>
<li>Does the text match this expression?</li>
<li>If so, where does it match?</li>
<li>Where did the capturing groups match?</li>
</ol>
<p>Generally speaking, this crate could provide a function to answer only #3,
which would subsume #1 and #2 automatically. However, it can be significantly
more expensive to compute the location of capturing group matches, so it's best
not to do it if you don't need to.</p>
<p>Therefore, only use what you need. For example, don't use <code>find</code> if you
only need to test if an expression matches a string. (Use <code>is_match</code>
instead.)</p>
<h1 id="unicode" class="section-header"><a href="#unicode">Unicode</a></h1>
<p>This implementation executes regular expressions <strong>only</strong> on valid UTF-8
while exposing match locations as byte indices into the search string.</p>
<p>Only simple case folding is supported. Namely, when matching
case-insensitively, the characters are first mapped using the &quot;simple&quot; case
folding rules defined by Unicode.</p>
<p>Regular expressions themselves are <strong>only</strong> interpreted as a sequence of
Unicode scalar values. This means you can use Unicode characters directly
in your expression:</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&quot;(?i)Δ+&quot;</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">&quot;ΔδΔ&quot;</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">0</span>, <span class="number">6</span>));</pre>
<p>Most features of the regular expressions in this crate are Unicode aware. Here
are some examples:</p>
<ul>
<li><code>.</code> will match any valid UTF-8 encoded Unicode scalar value except for <code>\n</code>.
(To also match <code>\n</code>, enable the <code>s</code> flag, e.g., <code>(?s:.)</code>.)</li>
<li><code>\w</code>, <code>\d</code> and <code>\s</code> are Unicode aware. For example, <code>\s</code> will match all forms
of whitespace categorized by Unicode.</li>
<li><code>\b</code> matches a Unicode word boundary.</li>
<li>Negated character classes like <code>[^a]</code> match all Unicode scalar values except
for <code>a</code>.</li>
<li><code>^</code> and <code>$</code> are <strong>not</strong> Unicode aware in multi-line mode. Namely, they only
recognize <code>\n</code> and not any of the other forms of line terminators defined
by Unicode.</li>
</ul>
<p>Unicode general categories, scripts, script extensions, ages and a smattering
of boolean properties are available as character classes. For example, you can
match a sequence of numerals, Greek or Cherokee letters:</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&quot;[\pN\p{Greek}\p{Cherokee}]+&quot;</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">&quot;abcΔᎠβⅠᏴγδⅡxyz&quot;</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">3</span>, <span class="number">23</span>));</pre>
<p>For a more detailed breakdown of Unicode support with respect to
<a href="http://unicode.org/reports/tr18/">UTS#18</a>,
please see the
<a href="https://github.com/rust-lang/regex/blob/master/UNICODE.md">UNICODE</a>
document in the root of the regex repository.</p>
<h1 id="opt-out-of-unicode-support" class="section-header"><a href="#opt-out-of-unicode-support">Opt out of Unicode support</a></h1>
<p>The <code>bytes</code> sub-module provides a <code>Regex</code> type that can be used to match
on <code>&amp;[u8]</code>. By default, text is interpreted as UTF-8 just like it is with
the main <code>Regex</code> type. However, this behavior can be disabled by turning
off the <code>u</code> flag, even if doing so could result in matching invalid UTF-8.
For example, when the <code>u</code> flag is disabled, <code>.</code> will match any byte instead
of any Unicode scalar value.</p>
<p>Disabling the <code>u</code> flag is also possible with the standard <code>&amp;str</code>-based <code>Regex</code>
type, but it is only allowed where the UTF-8 invariant is maintained. For
example, <code>(?-u:\w)</code> is an ASCII-only <code>\w</code> character class and is legal in an
<code>&amp;str</code>-based <code>Regex</code>, but <code>(?-u:\xFF)</code> will attempt to match the raw byte
<code>\xFF</code>, which is invalid UTF-8 and therefore is illegal in <code>&amp;str</code>-based
regexes.</p>
<h1 id="syntax" class="section-header"><a href="#syntax">Syntax</a></h1>
<p>The syntax supported in this crate is documented below.</p>
<p>Note that the regular expression parser and abstract syntax are exposed in
a separate crate, <a href="../regex_syntax/index.html"><code>regex-syntax</code></a>.</p>
<h2 id="matching-one-character" class="section-header"><a href="#matching-one-character">Matching one character</a></h2><pre class="rust">
. any character except new line (includes new line with s flag)
\d digit (\p{Nd})
\D not digit
\pN One-letter name Unicode character class
\p{Greek} Unicode character class (general category or script)
\PN Negated one-letter name Unicode character class
\P{Greek} negated Unicode character class (general category or script)
</pre>
<h3 id="character-classes" class="section-header"><a href="#character-classes">Character classes</a></h3><pre class="rust">
[xyz] A character class matching either x, y or z (union).
[^xyz] A character class matching any character except x, y and z.
[a-z] A character class matching any character in range a-z.
[[:alpha:]] ASCII character class ([A-Za-z])
[[:^alpha:]] Negated ASCII character class ([^A-Za-z])
[x[^xyz]] Nested/grouping character class (matching any character except y and z)
[a-y&&xyz] Intersection (matching x or y)
[0-9&&[^4]] Subtraction using intersection and negation (matching 0-9 except 4)
[0-9--4] Direct subtraction (matching 0-9 except 4)
[a-g~~b-h] Symmetric difference (matching `a` and `h` only)
[\[\]] Escaping in character classes (matching [ or ])
</pre>
<p>Any named character class may appear inside a bracketed <code>[...]</code> character
class. For example, <code>[\p{Greek}[:digit:]]</code> matches any Greek or ASCII
digit. <code>[\p{Greek}&amp;&amp;\pL]</code> matches Greek letters.</p>
<p>Precedence in character classes, from most binding to least:</p>
<ol>
<li>Ranges: <code>a-cd</code> == <code>[a-c]d</code></li>
<li>Union: <code>ab&amp;&amp;bc</code> == <code>[ab]&amp;&amp;[bc]</code></li>
<li>Intersection: <code>^a-z&amp;&amp;b</code> == <code>^[a-z&amp;&amp;b]</code></li>
<li>Negation</li>
</ol>
<h2 id="composites" class="section-header"><a href="#composites">Composites</a></h2><pre class="rust">
xy concatenation (x followed by y)
x|y alternation (x or y, prefer x)
</pre>
<h2 id="repetitions" class="section-header"><a href="#repetitions">Repetitions</a></h2><pre class="rust">
x* zero or more of x (greedy)
x+ one or more of x (greedy)
x? zero or one of x (greedy)
x*? zero or more of x (ungreedy/lazy)
x+? one or more of x (ungreedy/lazy)
x?? zero or one of x (ungreedy/lazy)
x{n,m} at least n x and at most m x (greedy)
x{n,} at least n x (greedy)
x{n} exactly n x
x{n,m}? at least n x and at most m x (ungreedy/lazy)
x{n,}? at least n x (ungreedy/lazy)
x{n}? exactly n x
</pre>
<h2 id="empty-matches" class="section-header"><a href="#empty-matches">Empty matches</a></h2><pre class="rust">
^ the beginning of text (or start-of-line with multi-line mode)
$ the end of text (or end-of-line with multi-line mode)
\A only the beginning of text (even with multi-line mode enabled)
\z only the end of text (even with multi-line mode enabled)
\b a Unicode word boundary (\w on one side and \W, \A, or \z on other)
\B not a Unicode word boundary
</pre>
<h2 id="grouping-and-flags" class="section-header"><a href="#grouping-and-flags">Grouping and flags</a></h2><pre class="rust">
(exp) numbered capture group (indexed by opening parenthesis)
(?P&lt;name&gt;exp) named (also numbered) capture group (allowed chars: [_0-9a-zA-Z])
(?:exp) non-capturing group
(?flags) set flags within current group
(?flags:exp) set flags for exp (non-capturing)
</pre>
<p>Flags are each a single character. For example, <code>(?x)</code> sets the flag <code>x</code>
and <code>(?-x)</code> clears the flag <code>x</code>. Multiple flags can be set or cleared at
the same time: <code>(?xy)</code> sets both the <code>x</code> and <code>y</code> flags and <code>(?x-y)</code> sets
the <code>x</code> flag and clears the <code>y</code> flag.</p>
<p>All flags are by default disabled unless stated otherwise. They are:</p>
<pre class="rust">
i case-insensitive: letters match both upper and lower case
m multi-line mode: ^ and $ match begin/end of line
s allow . to match \n
U swap the meaning of x* and x*?
u Unicode support (enabled by default)
x ignore whitespace and allow line comments (starting with `#`)
</pre>
<p>Flags can be toggled within a pattern. Here's an example that matches
case-insensitively for the first part but case-sensitively for the second part:</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&quot;(?i)a+(?-i)b+&quot;</span>).<span class="ident">unwrap</span>();
<span class="kw">let</span> <span class="ident">cap</span> <span class="op">=</span> <span class="ident">re</span>.<span class="ident">captures</span>(<span class="string">&quot;AaAaAbbBBBb&quot;</span>).<span class="ident">unwrap</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="ident">cap</span>[<span class="number">0</span>], <span class="string">&quot;AaAaAbb&quot;</span>);</pre>
<p>Notice that the <code>a+</code> matches either <code>a</code> or <code>A</code>, but the <code>b+</code> only matches
<code>b</code>.</p>
<p>Multi-line mode means <code>^</code> and <code>$</code> no longer match just at the beginning/end of
the input, but at the beginning/end of lines:</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&quot;(?m)^line \d+&quot;</span>).<span class="ident">unwrap</span>();
<span class="kw">let</span> <span class="ident">m</span> <span class="op">=</span> <span class="ident">re</span>.<span class="ident">find</span>(<span class="string">&quot;line one\nline 2\n&quot;</span>).<span class="ident">unwrap</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">m</span>.<span class="ident">as_str</span>(), <span class="string">&quot;line 2&quot;</span>);</pre>
<p>Note that <code>^</code> matches after new lines, even at the end of input:</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&quot;(?m)^&quot;</span>).<span class="ident">unwrap</span>();
<span class="kw">let</span> <span class="ident">m</span> <span class="op">=</span> <span class="ident">re</span>.<span class="ident">find_iter</span>(<span class="string">&quot;test\n&quot;</span>).<span class="ident">last</span>().<span class="ident">unwrap</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>((<span class="ident">m</span>.<span class="ident">start</span>(), <span class="ident">m</span>.<span class="ident">end</span>()), (<span class="number">5</span>, <span class="number">5</span>));</pre>
<p>Here is an example that uses an ASCII word boundary instead of a Unicode
word boundary:</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&quot;(?-u:\b).+(?-u:\b)&quot;</span>).<span class="ident">unwrap</span>();
<span class="kw">let</span> <span class="ident">cap</span> <span class="op">=</span> <span class="ident">re</span>.<span class="ident">captures</span>(<span class="string">&quot;$$abc$$&quot;</span>).<span class="ident">unwrap</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="ident">cap</span>[<span class="number">0</span>], <span class="string">&quot;abc&quot;</span>);</pre>
<h2 id="escape-sequences" class="section-header"><a href="#escape-sequences">Escape sequences</a></h2><pre class="rust">
\* literal *, works for any punctuation character: \.+*?()|[]{}^$
\a bell (\x07)
\f form feed (\x0C)
\t horizontal tab
\n new line
\r carriage return
\v vertical tab (\x0B)
\123 octal character code (up to three digits) (when enabled)
\x7F hex character code (exactly two digits)
\x{10FFFF} any hex character code corresponding to a Unicode code point
\u007F hex character code (exactly four digits)
\u{7F} any hex character code corresponding to a Unicode code point
\U0000007F hex character code (exactly eight digits)
\U{7F} any hex character code corresponding to a Unicode code point
</pre>
<h2 id="perl-character-classes-unicode-friendly" class="section-header"><a href="#perl-character-classes-unicode-friendly">Perl character classes (Unicode friendly)</a></h2>
<p>These classes are based on the definitions provided in
<a href="http://www.unicode.org/reports/tr18/#Compatibility_Properties">UTS#18</a>:</p>
<pre class="rust">
\d digit (\p{Nd})
\D not digit
\s whitespace (\p{White_Space})
\S not whitespace
\w word character (\p{Alphabetic} + \p{M} + \d + \p{Pc} + \p{Join_Control})
\W not word character
</pre>
<h2 id="ascii-character-classes" class="section-header"><a href="#ascii-character-classes">ASCII character classes</a></h2><pre class="rust">
[[:alnum:]] alphanumeric ([0-9A-Za-z])
[[:alpha:]] alphabetic ([A-Za-z])
[[:ascii:]] ASCII ([\x00-\x7F])
[[:blank:]] blank ([\t ])
[[:cntrl:]] control ([\x00-\x1F\x7F])
[[:digit:]] digits ([0-9])
[[:graph:]] graphical ([!-~])
[[:lower:]] lower case ([a-z])
[[:print:]] printable ([ -~])
[[:punct:]] punctuation ([!-/:-@\[-`{-~])
[[:space:]] whitespace ([\t\n\v\f\r ])
[[:upper:]] upper case ([A-Z])
[[:word:]] word characters ([0-9A-Za-z_])
[[:xdigit:]] hex digit ([0-9A-Fa-f])
</pre>
<h1 id="untrusted-input" class="section-header"><a href="#untrusted-input">Untrusted input</a></h1>
<p>This crate can handle both untrusted regular expressions and untrusted
search text.</p>
<p>Untrusted regular expressions are handled by capping the size of a compiled
regular expression.
(See <a href="struct.RegexBuilder.html#method.size_limit"><code>RegexBuilder::size_limit</code></a>.)
Without this, it would be trivial for an attacker to exhaust your system's
memory with expressions like <code>a{100}{100}{100}</code>.</p>
<p>Untrusted search text is allowed because the matching engine(s) in this
crate have time complexity <code>O(mn)</code> (with <code>m ~ regex</code> and <code>n ~ search text</code>), which means there's no way to cause exponential blow-up like with
some other regular expression engines. (We pay for this by disallowing
features like arbitrary look-ahead and backreferences.)</p>
<p>When a DFA is used, pathological cases with exponential state blow up are
avoided by constructing the DFA lazily or in an &quot;online&quot; manner. Therefore,
at most one new state can be created for each byte of input. This satisfies
our time complexity guarantees, but can lead to unbounded memory growth
proportional to the size of the input. As a stopgap, the DFA is only
allowed to store a fixed number of states. When the limit is reached, its
states are wiped and continues on, possibly duplicating previous work. If
the limit is reached too frequently, it gives up and hands control off to
another matching engine with fixed memory requirements.
(The DFA size limit can also be tweaked. See
<a href="struct.RegexBuilder.html#method.dfa_size_limit"><code>RegexBuilder::dfa_size_limit</code></a>.)</p>
</div><h2 id='modules' class='section-header'><a href="#modules">Modules</a></h2>
<table>
<tr class=' module-item'>
<td><a class="mod" href="bytes/index.html"
title='mod regex::bytes'>bytes</a></td>
<td class='docblock-short'>
<p>Match regular expressions on arbitrary bytes.</p>
</td>
</tr></table><h2 id='structs' class='section-header'><a href="#structs">Structs</a></h2>
<table>
<tr class=' module-item'>
<td><a class="struct" href="struct.CaptureMatches.html"
title='struct regex::CaptureMatches'>CaptureMatches</a></td>
<td class='docblock-short'>
<p>An iterator that yields all non-overlapping capture groups matching a
particular regular expression.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="struct" href="struct.CaptureNames.html"
title='struct regex::CaptureNames'>CaptureNames</a></td>
<td class='docblock-short'>
<p>An iterator over the names of all possible captures.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="struct" href="struct.Captures.html"
title='struct regex::Captures'>Captures</a></td>
<td class='docblock-short'>
<p>Captures represents a group of captured strings for a single match.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="struct" href="struct.Match.html"
title='struct regex::Match'>Match</a></td>
<td class='docblock-short'>
<p>Match represents a single match of a regex in a haystack.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="struct" href="struct.Matches.html"
title='struct regex::Matches'>Matches</a></td>
<td class='docblock-short'>
<p>An iterator over all non-overlapping matches for a particular string.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="struct" href="struct.NoExpand.html"
title='struct regex::NoExpand'>NoExpand</a></td>
<td class='docblock-short'>
<p><code>NoExpand</code> indicates literal string replacement.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="struct" href="struct.Regex.html"
title='struct regex::Regex'>Regex</a></td>
<td class='docblock-short'>
<p>A compiled regular expression for matching Unicode strings.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="struct" href="struct.RegexBuilder.html"
title='struct regex::RegexBuilder'>RegexBuilder</a></td>
<td class='docblock-short'>
<p>A configurable builder for a regular expression.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="struct" href="struct.RegexSet.html"
title='struct regex::RegexSet'>RegexSet</a></td>
<td class='docblock-short'>
<p>Match multiple (possibly overlapping) regular expressions in a single scan.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="struct" href="struct.RegexSetBuilder.html"
title='struct regex::RegexSetBuilder'>RegexSetBuilder</a></td>
<td class='docblock-short'>
<p>A configurable builder for a set of regular expressions.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="struct" href="struct.ReplacerRef.html"
title='struct regex::ReplacerRef'>ReplacerRef</a></td>
<td class='docblock-short'>
<p>By-reference adaptor for a <code>Replacer</code></p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="struct" href="struct.SetMatches.html"
title='struct regex::SetMatches'>SetMatches</a></td>
<td class='docblock-short'>
<p>A set of matches returned by a regex set.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="struct" href="struct.SetMatchesIntoIter.html"
title='struct regex::SetMatchesIntoIter'>SetMatchesIntoIter</a></td>
<td class='docblock-short'>
<p>An owned iterator over the set of matches from a regex set.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="struct" href="struct.SetMatchesIter.html"
title='struct regex::SetMatchesIter'>SetMatchesIter</a></td>
<td class='docblock-short'>
<p>A borrowed iterator over the set of matches from a regex set.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="struct" href="struct.Split.html"
title='struct regex::Split'>Split</a></td>
<td class='docblock-short'>
<p>Yields all substrings delimited by a regular expression match.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="struct" href="struct.SplitN.html"
title='struct regex::SplitN'>SplitN</a></td>
<td class='docblock-short'>
<p>Yields at most <code>N</code> substrings delimited by a regular expression match.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="struct" href="struct.SubCaptureMatches.html"
title='struct regex::SubCaptureMatches'>SubCaptureMatches</a></td>
<td class='docblock-short'>
<p>An iterator that yields all capturing matches in the order in which they
appear in the regex.</p>
</td>
</tr></table><h2 id='enums' class='section-header'><a href="#enums">Enums</a></h2>
<table>
<tr class=' module-item'>
<td><a class="enum" href="enum.Error.html"
title='enum regex::Error'>Error</a></td>
<td class='docblock-short'>
<p>An error that occurred during parsing or compiling a regular expression.</p>
</td>
</tr></table><h2 id='traits' class='section-header'><a href="#traits">Traits</a></h2>
<table>
<tr class=' module-item'>
<td><a class="trait" href="trait.Replacer.html"
title='trait regex::Replacer'>Replacer</a></td>
<td class='docblock-short'>
<p>Replacer describes types that can be used to replace matches in a string.</p>
</td>
</tr></table><h2 id='functions' class='section-header'><a href="#functions">Functions</a></h2>
<table>
<tr class=' module-item'>
<td><a class="fn" href="fn.escape.html"
title='fn regex::escape'>escape</a></td>
<td class='docblock-short'>
<p>Escapes all regular expression meta characters in <code>text</code>.</p>
</td>
</tr></table></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><kbd>?</kbd></dt>
<dd>Show this help dialog</dd>
<dt><kbd>S</kbd></dt>
<dd>Focus the search field</dd>
<dt><kbd>↑</kbd></dt>
<dd>Move up in search results</dd>
<dt><kbd>↓</kbd></dt>
<dd>Move down in search results</dd>
<dt><kbd>↹</kbd></dt>
<dd>Switch tab</dd>
<dt><kbd>&#9166;</kbd></dt>
<dd>Go to active search result</dd>
<dt><kbd>+</kbd></dt>
<dd>Expand all sections</dd>
<dt><kbd>-</kbd></dt>
<dd>Collapse 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="../main.js"></script>
<script defer src="../search-index.js"></script>
</body>
</html>
Reference in a new issue Copy permalink