<!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 `Error` struct in crate `std`."> <meta name="keywords" content="rust, rustlang, rust-lang, Error"> <title>std::io::Error - 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="../../main.css" id="themeStyle"> <script src="../../storage.js"></script> <link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"> </head> <body class="rustdoc struct"> <!--[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">☰</div> <a href='../../std/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a> <p class='location'>Struct Error</p><div class="sidebar-elems"><div class="block items"><a class="sidebar-title" href="#methods">Methods</a><div class="sidebar-links"><a href="#method.new">new</a><a href="#method.last_os_error">last_os_error</a><a href="#method.from_raw_os_error">from_raw_os_error</a><a href="#method.raw_os_error">raw_os_error</a><a href="#method.get_ref">get_ref</a><a href="#method.get_mut">get_mut</a><a href="#method.into_inner">into_inner</a><a href="#method.kind">kind</a></div><a class="sidebar-title" href="#implementations">Trait Implementations</a><div class="sidebar-links"><a href="#impl-From%3CNulError%3E">From<NulError></a><a href="#impl-From%3CIntoInnerError%3CW%3E%3E">From<IntoInnerError<W>></a><a href="#impl-Debug">Debug</a><a href="#impl-From%3CErrorKind%3E">From<ErrorKind></a><a href="#impl-Display">Display</a><a href="#impl-Error">Error</a></div></div><p class='location'><a href='../index.html'>std</a>::<wbr><a href='index.html'>io</a></p><script>window.sidebarCurrent = {name: 'Error', ty: 'struct', relpath: ''};</script><script defer src="sidebar-items.js"></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'>Struct <a href='../index.html'>std</a>::<wbr><a href='index.html'>io</a>::<wbr><a class="struct" href=''>Error</a></span><span class='out-of-band'><span class='since' title='Stable since Rust version 1.0.0'>1.0.0</span><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/std/io/error.rs.html#66-68' title='goto source code'>[src]</a></span></h1> <pre class='rust struct'>pub struct Error { /* fields omitted */ }</pre><div class='docblock'><p>The error type for I/O operations of the <a href="../io/trait.Read.html"><code>Read</code></a>, <a href="../io/trait.Write.html"><code>Write</code></a>, <a href="../io/trait.Seek.html"><code>Seek</code></a>, and associated traits.</p> <p>Errors mostly originate from the underlying OS, but custom instances of <code>Error</code> can be created with crafted error messages and a particular value of <a href="enum.ErrorKind.html"><code>ErrorKind</code></a>.</p> </div> <h2 id='methods' class='small-section-header'> Methods<a href='#methods' class='anchor'></a> </h2> <h3 id='impl' class='impl'><span class='in-band'><code>impl <a class="struct" href="../../std/io/struct.Error.html" title="struct std::io::Error">Error</a></code><a href='#impl' class='anchor'></a></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/io/error.rs.html#232-515' title='goto source code'>[src]</a></span></h3> <div class='impl-items'><h4 id='method.new' class="method"><span id='new.v' class='invisible'><code>pub fn <a href='#method.new' class='fnname'>new</a><E>(kind: <a class="enum" href="../../std/io/enum.ErrorKind.html" title="enum std::io::ErrorKind">ErrorKind</a>, error: E) -> <a class="struct" href="../../std/io/struct.Error.html" title="struct std::io::Error">Error</a> <span class="where fmt-newline">where<br> E: <a class="trait" href="../../std/convert/trait.Into.html" title="trait std::convert::Into">Into</a><<a class="struct" href="../../std/boxed/struct.Box.html" title="struct std::boxed::Box">Box</a><<a class="trait" href="../../std/error/trait.Error.html" title="trait std::error::Error">Error</a> + <a class="trait" href="../../std/marker/trait.Send.html" title="trait std::marker::Send">Send</a> + <a class="trait" href="../../std/marker/trait.Sync.html" title="trait std::marker::Sync">Sync</a>>>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/io/error.rs.html#252-256' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Creates a new I/O error from a known kind of error as well as an arbitrary error payload.</p> <p>This function is used to generically create I/O errors which do not originate from the OS itself. The <code>error</code> argument is an arbitrary payload which will be contained in this <code>Error</code>.</p> <h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">io</span>::{<span class="ident">Error</span>, <span class="ident">ErrorKind</span>}; <span class="comment">// errors can be created from strings</span> <span class="kw">let</span> <span class="ident">custom_error</span> <span class="op">=</span> <span class="ident">Error</span>::<span class="ident">new</span>(<span class="ident">ErrorKind</span>::<span class="ident">Other</span>, <span class="string">"oh no!"</span>); <span class="comment">// errors can also be created from other errors</span> <span class="kw">let</span> <span class="ident">custom_error2</span> <span class="op">=</span> <span class="ident">Error</span>::<span class="ident">new</span>(<span class="ident">ErrorKind</span>::<span class="ident">Interrupted</span>, <span class="ident">custom_error</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Aio%3A%3A%7BError%2C%20ErrorKind%7D%3B%0A%0A%2F%2F%20errors%20can%20be%20created%20from%20strings%0Alet%20custom_error%20%3D%20Error%3A%3Anew(ErrorKind%3A%3AOther%2C%20%22oh%20no!%22)%3B%0A%0A%2F%2F%20errors%20can%20also%20be%20created%20from%20other%20errors%0Alet%20custom_error2%20%3D%20Error%3A%3Anew(ErrorKind%3A%3AInterrupted%2C%20custom_error)%3B%0A%7D">Run</a></pre> </div><h4 id='method.last_os_error' class="method"><span id='last_os_error.v' class='invisible'><code>pub fn <a href='#method.last_os_error' class='fnname'>last_os_error</a>() -> <a class="struct" href="../../std/io/struct.Error.html" title="struct std::io::Error">Error</a></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/io/error.rs.html#281-283' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Returns an error representing the last OS error which occurred.</p> <p>This function reads the value of <code>errno</code> for the target platform (e.g. <code>GetLastError</code> on Windows) and will return a corresponding instance of <code>Error</code> for the error code.</p> <h1 id="examples-1" class="section-header"><a href="#examples-1">Examples</a></h1> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">io</span>::<span class="ident">Error</span>; <span class="macro">println</span><span class="macro">!</span>(<span class="string">"last OS error: {:?}"</span>, <span class="ident">Error</span>::<span class="ident">last_os_error</span>());<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Aio%3A%3AError%3B%0A%0Aprintln!(%22last%20OS%20error%3A%20%7B%3A%3F%7D%22%2C%20Error%3A%3Alast_os_error())%3B%0A%7D">Run</a></pre> </div><h4 id='method.from_raw_os_error' class="method"><span id='from_raw_os_error.v' class='invisible'><code>pub fn <a href='#method.from_raw_os_error' class='fnname'>from_raw_os_error</a>(code: <a class="primitive" href="../primitive.i32.html">i32</a>) -> <a class="struct" href="../../std/io/struct.Error.html" title="struct std::io::Error">Error</a></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/io/error.rs.html#311-313' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Creates a new instance of an <code>Error</code> from a particular OS error code.</p> <h1 id="examples-2" class="section-header"><a href="#examples-2">Examples</a></h1> <p>On Linux:</p> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">io</span>; <span class="kw">let</span> <span class="ident">error</span> <span class="op">=</span> <span class="ident">io</span>::<span class="ident">Error</span>::<span class="ident">from_raw_os_error</span>(<span class="number">22</span>); <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">error</span>.<span class="ident">kind</span>(), <span class="ident">io</span>::<span class="ident">ErrorKind</span>::<span class="ident">InvalidInput</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Aif%20cfg!(target_os%20%3D%20%22linux%22)%20%7B%0Ause%20std%3A%3Aio%3B%0A%0Alet%20error%20%3D%20io%3A%3AError%3A%3Afrom_raw_os_error(22)%3B%0Aassert_eq!(error.kind()%2C%20io%3A%3AErrorKind%3A%3AInvalidInput)%3B%0A%7D%0A%7D">Run</a></pre> <p>On Windows:</p> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">io</span>; <span class="kw">let</span> <span class="ident">error</span> <span class="op">=</span> <span class="ident">io</span>::<span class="ident">Error</span>::<span class="ident">from_raw_os_error</span>(<span class="number">10022</span>); <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">error</span>.<span class="ident">kind</span>(), <span class="ident">io</span>::<span class="ident">ErrorKind</span>::<span class="ident">InvalidInput</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Aif%20cfg!(windows)%20%7B%0Ause%20std%3A%3Aio%3B%0A%0Alet%20error%20%3D%20io%3A%3AError%3A%3Afrom_raw_os_error(10022)%3B%0Aassert_eq!(error.kind()%2C%20io%3A%3AErrorKind%3A%3AInvalidInput)%3B%0A%7D%0A%7D">Run</a></pre> </div><h4 id='method.raw_os_error' class="method"><span id='raw_os_error.v' class='invisible'><code>pub fn <a href='#method.raw_os_error' class='fnname'>raw_os_error</a>(&self) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><<a class="primitive" href="../primitive.i32.html">i32</a>></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/io/error.rs.html#342-348' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Returns the OS error that this error represents (if any).</p> <p>If this <code>Error</code> was constructed via <code>last_os_error</code> or <code>from_raw_os_error</code>, then this function will return <code>Some</code>, otherwise it will return <code>None</code>.</p> <h1 id="examples-3" class="section-header"><a href="#examples-3">Examples</a></h1> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">io</span>::{<span class="ident">Error</span>, <span class="ident">ErrorKind</span>}; <span class="kw">fn</span> <span class="ident">print_os_error</span>(<span class="ident">err</span>: <span class="kw-2">&</span><span class="ident">Error</span>) { <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">raw_os_err</span>) <span class="op">=</span> <span class="ident">err</span>.<span class="ident">raw_os_error</span>() { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"raw OS error: {:?}"</span>, <span class="ident">raw_os_err</span>); } <span class="kw">else</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Not an OS error"</span>); } } <span class="kw">fn</span> <span class="ident">main</span>() { <span class="comment">// Will print "raw OS error: ...".</span> <span class="ident">print_os_error</span>(<span class="kw-2">&</span><span class="ident">Error</span>::<span class="ident">last_os_error</span>()); <span class="comment">// Will print "Not an OS error".</span> <span class="ident">print_os_error</span>(<span class="kw-2">&</span><span class="ident">Error</span>::<span class="ident">new</span>(<span class="ident">ErrorKind</span>::<span class="ident">Other</span>, <span class="string">"oh no!"</span>)); }<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Ause%20std%3A%3Aio%3A%3A%7BError%2C%20ErrorKind%7D%3B%0A%0Afn%20print_os_error(err%3A%20%26Error)%20%7B%0A%20%20%20%20if%20let%20Some(raw_os_err)%20%3D%20err.raw_os_error()%20%7B%0A%20%20%20%20%20%20%20%20println!(%22raw%20OS%20error%3A%20%7B%3A%3F%7D%22%2C%20raw_os_err)%3B%0A%20%20%20%20%7D%20else%20%7B%0A%20%20%20%20%20%20%20%20println!(%22Not%20an%20OS%20error%22)%3B%0A%20%20%20%20%7D%0A%7D%0A%0Afn%20main()%20%7B%0A%20%20%20%20%2F%2F%20Will%20print%20%22raw%20OS%20error%3A%20...%22.%0A%20%20%20%20print_os_error(%26Error%3A%3Alast_os_error())%3B%0A%20%20%20%20%2F%2F%20Will%20print%20%22Not%20an%20OS%20error%22.%0A%20%20%20%20print_os_error(%26Error%3A%3Anew(ErrorKind%3A%3AOther%2C%20%22oh%20no!%22))%3B%0A%7D%0A">Run</a></pre> </div><h4 id='method.get_ref' class="method"><span id='get_ref.v' class='invisible'><code>pub fn <a href='#method.get_ref' class='fnname'>get_ref</a>(&self) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><&(<a class="trait" href="../../std/error/trait.Error.html" title="trait std::error::Error">Error</a> + <a class="trait" href="../../std/marker/trait.Send.html" title="trait std::marker::Send">Send</a> + <a class="trait" href="../../std/marker/trait.Sync.html" title="trait std::marker::Sync">Sync</a> + 'static)></code></span><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.3.0'>1.3.0</div><a class='srclink' href='../../src/std/io/error.rs.html#376-382' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Returns a reference to the inner error wrapped by this error (if any).</p> <p>If this <code>Error</code> was constructed via <code>new</code> then this function will return <code>Some</code>, otherwise it will return <code>None</code>.</p> <h1 id="examples-4" class="section-header"><a href="#examples-4">Examples</a></h1> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">io</span>::{<span class="ident">Error</span>, <span class="ident">ErrorKind</span>}; <span class="kw">fn</span> <span class="ident">print_error</span>(<span class="ident">err</span>: <span class="kw-2">&</span><span class="ident">Error</span>) { <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">inner_err</span>) <span class="op">=</span> <span class="ident">err</span>.<span class="ident">get_ref</span>() { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Inner error: {:?}"</span>, <span class="ident">inner_err</span>); } <span class="kw">else</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"No inner error"</span>); } } <span class="kw">fn</span> <span class="ident">main</span>() { <span class="comment">// Will print "No inner error".</span> <span class="ident">print_error</span>(<span class="kw-2">&</span><span class="ident">Error</span>::<span class="ident">last_os_error</span>()); <span class="comment">// Will print "Inner error: ...".</span> <span class="ident">print_error</span>(<span class="kw-2">&</span><span class="ident">Error</span>::<span class="ident">new</span>(<span class="ident">ErrorKind</span>::<span class="ident">Other</span>, <span class="string">"oh no!"</span>)); }<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Ause%20std%3A%3Aio%3A%3A%7BError%2C%20ErrorKind%7D%3B%0A%0Afn%20print_error(err%3A%20%26Error)%20%7B%0A%20%20%20%20if%20let%20Some(inner_err)%20%3D%20err.get_ref()%20%7B%0A%20%20%20%20%20%20%20%20println!(%22Inner%20error%3A%20%7B%3A%3F%7D%22%2C%20inner_err)%3B%0A%20%20%20%20%7D%20else%20%7B%0A%20%20%20%20%20%20%20%20println!(%22No%20inner%20error%22)%3B%0A%20%20%20%20%7D%0A%7D%0A%0Afn%20main()%20%7B%0A%20%20%20%20%2F%2F%20Will%20print%20%22No%20inner%20error%22.%0A%20%20%20%20print_error(%26Error%3A%3Alast_os_error())%3B%0A%20%20%20%20%2F%2F%20Will%20print%20%22Inner%20error%3A%20...%22.%0A%20%20%20%20print_error(%26Error%3A%3Anew(ErrorKind%3A%3AOther%2C%20%22oh%20no!%22))%3B%0A%7D%0A">Run</a></pre> </div><h4 id='method.get_mut' class="method"><span id='get_mut.v' class='invisible'><code>pub fn <a href='#method.get_mut' class='fnname'>get_mut</a>(&mut self) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><&mut (<a class="trait" href="../../std/error/trait.Error.html" title="trait std::error::Error">Error</a> + <a class="trait" href="../../std/marker/trait.Send.html" title="trait std::marker::Send">Send</a> + <a class="trait" href="../../std/marker/trait.Sync.html" title="trait std::marker::Sync">Sync</a> + 'static)></code></span><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.3.0'>1.3.0</div><a class='srclink' href='../../src/std/io/error.rs.html#447-453' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Returns a mutable reference to the inner error wrapped by this error (if any).</p> <p>If this <code>Error</code> was constructed via <code>new</code> then this function will return <code>Some</code>, otherwise it will return <code>None</code>.</p> <h1 id="examples-5" class="section-header"><a href="#examples-5">Examples</a></h1> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">io</span>::{<span class="ident">Error</span>, <span class="ident">ErrorKind</span>}; <span class="kw">use</span> <span class="ident">std</span>::{<span class="ident">error</span>, <span class="ident">fmt</span>}; <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>::<span class="ident">Display</span>; <span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span> <span class="kw">struct</span> <span class="ident">MyError</span> { <span class="ident">v</span>: <span class="ident">String</span>, } <span class="kw">impl</span> <span class="ident">MyError</span> { <span class="kw">fn</span> <span class="ident">new</span>() <span class="op">-></span> <span class="ident">MyError</span> { <span class="ident">MyError</span> { <span class="ident">v</span>: <span class="string">"oh no!"</span>.<span class="ident">to_string</span>() } } <span class="kw">fn</span> <span class="ident">change_message</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">new_message</span>: <span class="kw-2">&</span><span class="ident">str</span>) { <span class="self">self</span>.<span class="ident">v</span> <span class="op">=</span> <span class="ident">new_message</span>.<span class="ident">to_string</span>(); } } <span class="kw">impl</span> <span class="ident">error</span>::<span class="ident">Error</span> <span class="kw">for</span> <span class="ident">MyError</span> { <span class="kw">fn</span> <span class="ident">description</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">str</span> { <span class="kw-2">&</span><span class="self">self</span>.<span class="ident">v</span> } } <span class="kw">impl</span> <span class="ident">Display</span> <span class="kw">for</span> <span class="ident">MyError</span> { <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">f</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-></span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> { <span class="macro">write</span><span class="macro">!</span>(<span class="ident">f</span>, <span class="string">"MyError: {}"</span>, <span class="kw-2">&</span><span class="self">self</span>.<span class="ident">v</span>) } } <span class="kw">fn</span> <span class="ident">change_error</span>(<span class="kw-2">mut</span> <span class="ident">err</span>: <span class="ident">Error</span>) <span class="op">-></span> <span class="ident">Error</span> { <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">inner_err</span>) <span class="op">=</span> <span class="ident">err</span>.<span class="ident">get_mut</span>() { <span class="ident">inner_err</span>.<span class="ident">downcast_mut</span>::<span class="op"><</span><span class="ident">MyError</span><span class="op">></span>().<span class="ident">unwrap</span>().<span class="ident">change_message</span>(<span class="string">"I've been changed!"</span>); } <span class="ident">err</span> } <span class="kw">fn</span> <span class="ident">print_error</span>(<span class="ident">err</span>: <span class="kw-2">&</span><span class="ident">Error</span>) { <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">inner_err</span>) <span class="op">=</span> <span class="ident">err</span>.<span class="ident">get_ref</span>() { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Inner error: {}"</span>, <span class="ident">inner_err</span>); } <span class="kw">else</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"No inner error"</span>); } } <span class="kw">fn</span> <span class="ident">main</span>() { <span class="comment">// Will print "No inner error".</span> <span class="ident">print_error</span>(<span class="kw-2">&</span><span class="ident">change_error</span>(<span class="ident">Error</span>::<span class="ident">last_os_error</span>())); <span class="comment">// Will print "Inner error: ...".</span> <span class="ident">print_error</span>(<span class="kw-2">&</span><span class="ident">change_error</span>(<span class="ident">Error</span>::<span class="ident">new</span>(<span class="ident">ErrorKind</span>::<span class="ident">Other</span>, <span class="ident">MyError</span>::<span class="ident">new</span>()))); }<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Ause%20std%3A%3Aio%3A%3A%7BError%2C%20ErrorKind%7D%3B%0Ause%20std%3A%3A%7Berror%2C%20fmt%7D%3B%0Ause%20std%3A%3Afmt%3A%3ADisplay%3B%0A%0A%23%5Bderive(Debug)%5D%0Astruct%20MyError%20%7B%0A%20%20%20%20v%3A%20String%2C%0A%7D%0A%0Aimpl%20MyError%20%7B%0A%20%20%20%20fn%20new()%20-%3E%20MyError%20%7B%0A%20%20%20%20%20%20%20%20MyError%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20v%3A%20%22oh%20no!%22.to_string()%0A%20%20%20%20%20%20%20%20%7D%0A%20%20%20%20%7D%0A%0A%20%20%20%20fn%20change_message(%26mut%20self%2C%20new_message%3A%20%26str)%20%7B%0A%20%20%20%20%20%20%20%20self.v%20%3D%20new_message.to_string()%3B%0A%20%20%20%20%7D%0A%7D%0A%0Aimpl%20error%3A%3AError%20for%20MyError%20%7B%0A%20%20%20%20fn%20description(%26self)%20-%3E%20%26str%20%7B%20%26self.v%20%7D%0A%7D%0A%0Aimpl%20Display%20for%20MyError%20%7B%0A%20%20%20%20fn%20fmt(%26self%2C%20f%3A%20%26mut%20fmt%3A%3AFormatter)%20-%3E%20fmt%3A%3AResult%20%7B%0A%20%20%20%20%20%20%20%20write!(f%2C%20%22MyError%3A%20%7B%7D%22%2C%20%26self.v)%0A%20%20%20%20%7D%0A%7D%0A%0Afn%20change_error(mut%20err%3A%20Error)%20-%3E%20Error%20%7B%0A%20%20%20%20if%20let%20Some(inner_err)%20%3D%20err.get_mut()%20%7B%0A%20%20%20%20%20%20%20%20inner_err.downcast_mut%3A%3A%3CMyError%3E().unwrap().change_message(%22I've%20been%20changed!%22)%3B%0A%20%20%20%20%7D%0A%20%20%20%20err%0A%7D%0A%0Afn%20print_error(err%3A%20%26Error)%20%7B%0A%20%20%20%20if%20let%20Some(inner_err)%20%3D%20err.get_ref()%20%7B%0A%20%20%20%20%20%20%20%20println!(%22Inner%20error%3A%20%7B%7D%22%2C%20inner_err)%3B%0A%20%20%20%20%7D%20else%20%7B%0A%20%20%20%20%20%20%20%20println!(%22No%20inner%20error%22)%3B%0A%20%20%20%20%7D%0A%7D%0A%0Afn%20main()%20%7B%0A%20%20%20%20%2F%2F%20Will%20print%20%22No%20inner%20error%22.%0A%20%20%20%20print_error(%26change_error(Error%3A%3Alast_os_error()))%3B%0A%20%20%20%20%2F%2F%20Will%20print%20%22Inner%20error%3A%20...%22.%0A%20%20%20%20print_error(%26change_error(Error%3A%3Anew(ErrorKind%3A%3AOther%2C%20MyError%3A%3Anew())))%3B%0A%7D%0A">Run</a></pre> </div><h4 id='method.into_inner' class="method"><span id='into_inner.v' class='invisible'><code>pub fn <a href='#method.into_inner' class='fnname'>into_inner</a>(self) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><<a class="struct" href="../../std/boxed/struct.Box.html" title="struct std::boxed::Box">Box</a><<a class="trait" href="../../std/error/trait.Error.html" title="trait std::error::Error">Error</a> + <a class="trait" href="../../std/marker/trait.Send.html" title="trait std::marker::Send">Send</a> + <a class="trait" href="../../std/marker/trait.Sync.html" title="trait std::marker::Sync">Sync</a>>></code></span><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.3.0'>1.3.0</div><a class='srclink' href='../../src/std/io/error.rs.html#481-487' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Consumes the <code>Error</code>, returning its inner error (if any).</p> <p>If this <code>Error</code> was constructed via <code>new</code> then this function will return <code>Some</code>, otherwise it will return <code>None</code>.</p> <h1 id="examples-6" class="section-header"><a href="#examples-6">Examples</a></h1> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">io</span>::{<span class="ident">Error</span>, <span class="ident">ErrorKind</span>}; <span class="kw">fn</span> <span class="ident">print_error</span>(<span class="ident">err</span>: <span class="ident">Error</span>) { <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">inner_err</span>) <span class="op">=</span> <span class="ident">err</span>.<span class="ident">into_inner</span>() { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Inner error: {}"</span>, <span class="ident">inner_err</span>); } <span class="kw">else</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"No inner error"</span>); } } <span class="kw">fn</span> <span class="ident">main</span>() { <span class="comment">// Will print "No inner error".</span> <span class="ident">print_error</span>(<span class="ident">Error</span>::<span class="ident">last_os_error</span>()); <span class="comment">// Will print "Inner error: ...".</span> <span class="ident">print_error</span>(<span class="ident">Error</span>::<span class="ident">new</span>(<span class="ident">ErrorKind</span>::<span class="ident">Other</span>, <span class="string">"oh no!"</span>)); }<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Ause%20std%3A%3Aio%3A%3A%7BError%2C%20ErrorKind%7D%3B%0A%0Afn%20print_error(err%3A%20Error)%20%7B%0A%20%20%20%20if%20let%20Some(inner_err)%20%3D%20err.into_inner()%20%7B%0A%20%20%20%20%20%20%20%20println!(%22Inner%20error%3A%20%7B%7D%22%2C%20inner_err)%3B%0A%20%20%20%20%7D%20else%20%7B%0A%20%20%20%20%20%20%20%20println!(%22No%20inner%20error%22)%3B%0A%20%20%20%20%7D%0A%7D%0A%0Afn%20main()%20%7B%0A%20%20%20%20%2F%2F%20Will%20print%20%22No%20inner%20error%22.%0A%20%20%20%20print_error(Error%3A%3Alast_os_error())%3B%0A%20%20%20%20%2F%2F%20Will%20print%20%22Inner%20error%3A%20...%22.%0A%20%20%20%20print_error(Error%3A%3Anew(ErrorKind%3A%3AOther%2C%20%22oh%20no!%22))%3B%0A%7D%0A">Run</a></pre> </div><h4 id='method.kind' class="method"><span id='kind.v' class='invisible'><code>pub fn <a href='#method.kind' class='fnname'>kind</a>(&self) -> <a class="enum" href="../../std/io/enum.ErrorKind.html" title="enum std::io::ErrorKind">ErrorKind</a></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/io/error.rs.html#508-514' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Returns the corresponding <code>ErrorKind</code> for this error.</p> <h1 id="examples-7" class="section-header"><a href="#examples-7">Examples</a></h1> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">io</span>::{<span class="ident">Error</span>, <span class="ident">ErrorKind</span>}; <span class="kw">fn</span> <span class="ident">print_error</span>(<span class="ident">err</span>: <span class="ident">Error</span>) { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"{:?}"</span>, <span class="ident">err</span>.<span class="ident">kind</span>()); } <span class="kw">fn</span> <span class="ident">main</span>() { <span class="comment">// Will print "No inner error".</span> <span class="ident">print_error</span>(<span class="ident">Error</span>::<span class="ident">last_os_error</span>()); <span class="comment">// Will print "Inner error: ...".</span> <span class="ident">print_error</span>(<span class="ident">Error</span>::<span class="ident">new</span>(<span class="ident">ErrorKind</span>::<span class="ident">AddrInUse</span>, <span class="string">"oh no!"</span>)); }<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Ause%20std%3A%3Aio%3A%3A%7BError%2C%20ErrorKind%7D%3B%0A%0Afn%20print_error(err%3A%20Error)%20%7B%0A%20%20%20%20println!(%22%7B%3A%3F%7D%22%2C%20err.kind())%3B%0A%7D%0A%0Afn%20main()%20%7B%0A%20%20%20%20%2F%2F%20Will%20print%20%22No%20inner%20error%22.%0A%20%20%20%20print_error(Error%3A%3Alast_os_error())%3B%0A%20%20%20%20%2F%2F%20Will%20print%20%22Inner%20error%3A%20...%22.%0A%20%20%20%20print_error(Error%3A%3Anew(ErrorKind%3A%3AAddrInUse%2C%20%22oh%20no!%22))%3B%0A%7D%0A">Run</a></pre> </div></div> <h2 id='implementations' class='small-section-header'> Trait Implementations<a href='#implementations' class='anchor'></a> </h2> <h3 id='impl-From%3CNulError%3E' class='impl'><span class='in-band'><code>impl <a class="trait" href="../../std/convert/trait.From.html" title="trait std::convert::From">From</a><<a class="struct" href="../../std/ffi/struct.NulError.html" title="struct std::ffi::NulError">NulError</a>> for <a class="struct" href="../../std/io/struct.Error.html" title="struct std::io::Error">Error</a></code><a href='#impl-From%3CNulError%3E' class='anchor'></a></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/ffi/c_str.rs.html#801-806' title='goto source code'>[src]</a></span></h3> <div class='impl-items'><h4 id='method.from' class="method"><span id='from.v' class='invisible'><code>fn <a href='../../std/convert/trait.From.html#tymethod.from' class='fnname'>from</a>(_: <a class="struct" href="../../std/ffi/struct.NulError.html" title="struct std::ffi::NulError">NulError</a>) -> <a class="struct" href="../../std/io/struct.Error.html" title="struct std::io::Error">Error</a></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/ffi/c_str.rs.html#802-805' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Performs the conversion.</p> </div></div><h3 id='impl-From%3CIntoInnerError%3CW%3E%3E' class='impl'><span class='in-band'><code>impl<W> <a class="trait" href="../../std/convert/trait.From.html" title="trait std::convert::From">From</a><<a class="struct" href="../../std/io/struct.IntoInnerError.html" title="struct std::io::IntoInnerError">IntoInnerError</a><W>> for <a class="struct" href="../../std/io/struct.Error.html" title="struct std::io::Error">Error</a></code><a href='#impl-From%3CIntoInnerError%3CW%3E%3E' class='anchor'></a></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/io/buffered.rs.html#659-661' title='goto source code'>[src]</a></span></h3> <div class='impl-items'><h4 id='method.from-1' class="method"><span id='from.v-1' class='invisible'><code>fn <a href='../../std/convert/trait.From.html#tymethod.from' class='fnname'>from</a>(iie: <a class="struct" href="../../std/io/struct.IntoInnerError.html" title="struct std::io::IntoInnerError">IntoInnerError</a><W>) -> <a class="struct" href="../../std/io/struct.Error.html" title="struct std::io::Error">Error</a></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/io/buffered.rs.html#660' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Performs the conversion.</p> </div></div><h3 id='impl-Debug' class='impl'><span class='in-band'><code>impl <a class="trait" href="../../std/fmt/trait.Debug.html" title="trait std::fmt::Debug">Debug</a> for <a class="struct" href="../../std/io/struct.Error.html" title="struct std::io::Error">Error</a></code><a href='#impl-Debug' class='anchor'></a></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/io/error.rs.html#71-75' 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='../../std/fmt/trait.Debug.html#tymethod.fmt' class='fnname'>fmt</a>(&self, f: &mut <a class="struct" href="../../std/fmt/struct.Formatter.html" title="struct std::fmt::Formatter">Formatter</a>) -> <a class="type" href="../../std/fmt/type.Result.html" title="type std::fmt::Result">Result</a></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/io/error.rs.html#72-74' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Formats the value using the given formatter. <a href="../../std/fmt/trait.Debug.html#tymethod.fmt">Read more</a></p> </div></div><h3 id='impl-From%3CErrorKind%3E' class='impl'><span class='in-band'><code>impl <a class="trait" href="../../std/convert/trait.From.html" title="trait std::convert::From">From</a><<a class="enum" href="../../std/io/enum.ErrorKind.html" title="enum std::io::ErrorKind">ErrorKind</a>> for <a class="struct" href="../../std/io/struct.Error.html" title="struct std::io::Error">Error</a></code><a href='#impl-From%3CErrorKind%3E' class='anchor'></a></span><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.14.0'>1.14.0</div><a class='srclink' href='../../src/std/io/error.rs.html#223-230' title='goto source code'>[src]</a></span></h3> <div class='docblock'><p>Intended for use for errors not exposed to the user, where allocating onto the heap (for normal construction via Error::new) is too costly.</p> </div><div class='impl-items'><h4 id='method.from-2' class="method"><span id='from.v-2' class='invisible'><code>fn <a href='../../std/convert/trait.From.html#tymethod.from' class='fnname'>from</a>(kind: <a class="enum" href="../../std/io/enum.ErrorKind.html" title="enum std::io::ErrorKind">ErrorKind</a>) -> <a class="struct" href="../../std/io/struct.Error.html" title="struct std::io::Error">Error</a></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/io/error.rs.html#225-229' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Performs the conversion.</p> </div></div><h3 id='impl-Display' class='impl'><span class='in-band'><code>impl <a class="trait" href="../../std/fmt/trait.Display.html" title="trait std::fmt::Display">Display</a> for <a class="struct" href="../../std/io/struct.Error.html" title="struct std::io::Error">Error</a></code><a href='#impl-Display' class='anchor'></a></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/io/error.rs.html#532-543' 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='../../std/fmt/trait.Display.html#tymethod.fmt' class='fnname'>fmt</a>(&self, fmt: &mut <a class="struct" href="../../std/fmt/struct.Formatter.html" title="struct std::fmt::Formatter">Formatter</a>) -> <a class="type" href="../../std/fmt/type.Result.html" title="type std::fmt::Result">Result</a></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/io/error.rs.html#533-542' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Formats the value using the given formatter. <a href="../../std/fmt/trait.Display.html#tymethod.fmt">Read more</a></p> </div></div><h3 id='impl-Error' class='impl'><span class='in-band'><code>impl <a class="trait" href="../../std/error/trait.Error.html" title="trait std::error::Error">Error</a> for <a class="struct" href="../../std/io/struct.Error.html" title="struct std::io::Error">Error</a></code><a href='#impl-Error' class='anchor'></a></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/io/error.rs.html#546-561' title='goto source code'>[src]</a></span></h3> <div class='impl-items'><h4 id='method.description' class="method"><span id='description.v' class='invisible'><code>fn <a href='../../std/error/trait.Error.html#tymethod.description' class='fnname'>description</a>(&self) -> &<a class="primitive" href="../primitive.str.html">str</a></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/io/error.rs.html#547-552' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>A short description of the error. <a href="../../std/error/trait.Error.html#tymethod.description">Read more</a></p> </div><h4 id='method.cause' class="method"><span id='cause.v' class='invisible'><code>fn <a href='../../std/error/trait.Error.html#method.cause' class='fnname'>cause</a>(&self) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><&<a class="trait" href="../../std/error/trait.Error.html" title="trait std::error::Error">Error</a>></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/io/error.rs.html#554-560' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>The lower-level cause of this error, if any. <a href="../../std/error/trait.Error.html#method.cause">Read more</a></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><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>⏎</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 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