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<h1 class='fqn'><span class='in-band'>Function <a href='../index.html'>std</a>::<wbr><a href='index.html'>io</a>::<wbr><a class="fn" href=''>copy</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'>
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</span><a class='srclink' href='../../src/std/io/util.rs.html#49-69' title='goto source code'>[src]</a></span></h1>
<pre class='rust fn'>pub fn copy<R: ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, W: ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>>(reader: <a class="primitive" href="../primitive.reference.html">&mut </a>R, writer: <a class="primitive" href="../primitive.reference.html">&mut </a>W) -> <a class="type" href="../../std/io/type.Result.html" title="type std::io::Result">Result</a><<a class="primitive" href="../primitive.u64.html">u64</a>> <span class="where fmt-newline">where<br> R: <a class="trait" href="../../std/io/trait.Read.html" title="trait std::io::Read">Read</a>,<br> W: <a class="trait" href="../../std/io/trait.Write.html" title="trait std::io::Write">Write</a>, </span></pre><div class='docblock'><p>Copies the entire contents of a reader into a writer.</p>
<p>This function will continuously read data from <code>reader</code> and then
write it into <code>writer</code> in a streaming fashion until <code>reader</code>
returns EOF.</p>
<p>On success, the total number of bytes that were copied from
<code>reader</code> to <code>writer</code> is returned.</p>
<h1 id="errors" class="section-header"><a href="#errors">Errors</a></h1>
<p>This function will return an error immediately if any call to <code>read</code> or
<code>write</code> returns an error. All instances of <code>ErrorKind::Interrupted</code> are
handled by this function and the underlying operation is retried.</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="kw">let</span> <span class="kw-2">mut</span> <span class="ident">reader</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>] <span class="op">=</span> <span class="string">b"hello"</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">writer</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[];
<span class="ident">io</span>::<span class="ident">copy</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">reader</span>, <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">writer</span>)<span class="question-mark">?</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&</span><span class="string">b"hello"</span>[..], <span class="kw-2">&</span><span class="ident">writer</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%3B%0A%0Afn%20foo()%20-%3E%20io%3A%3AResult%3C()%3E%20%7B%0Alet%20mut%20reader%3A%20%26%5Bu8%5D%20%3D%20b%22hello%22%3B%0Alet%20mut%20writer%3A%20Vec%3Cu8%3E%20%3D%20vec!%5B%5D%3B%0A%0Aio%3A%3Acopy(%26mut%20reader%2C%20%26mut%20writer)%3F%3B%0A%0Aassert_eq!(%26b%22hello%22%5B..%5D%2C%20%26writer%5B..%5D)%3B%0AOk(())%0A%7D%0Afoo().unwrap()%3B%0A%7D">Run</a></pre>
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