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<p class='location'><a href='../../index.html'>bitflags</a>::<wbr><a href='../index.html'>__core</a>::<wbr><a href='index.html'>fs</a></p><script>window.sidebarCurrent = {name: 'OpenOptions', ty: 'struct', relpath: ''};</script><script defer src="sidebar-items.js"></script>
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<section id='main' class="content struct">
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<h1 class='fqn'><span class='in-band'>Struct <a href='../../index.html'>bitflags</a>::<wbr><a href='../index.html'>__core</a>::<wbr><a href='index.html'>fs</a>::<wbr><a class='struct' href=''>OpenOptions</a></span><span class='out-of-band'><span id='render-detail'>
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[<span class='inner'>−</span>]
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</span><a id='src-3614' class='srclink' href='https://doc.rust-lang.org/nightly/std/fs/struct.OpenOptions.html?gotosrc=3614' title='goto source code'>[src]</a></span></h1>
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<pre class='rust struct'>pub struct OpenOptions(_);</pre><span class="since">1.0.0</span><div class='docblock'><p>Options and flags which can be used to configure how a file is opened.</p>
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<p>This builder exposes the ability to configure how a <code>File</code> is opened and
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what operations are permitted on the open file. The <code>File::open</code> and
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<code>File::create</code> methods are aliases for commonly used options using this
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builder.</p>
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<p>Generally speaking, when using <code>OpenOptions</code>, you'll first call <code>new()</code>,
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then chain calls to methods to set each option, then call <code>open()</code>, passing
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the path of the file you're trying to open. This will give you a
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<a href="../io/type.Result.html"><code>io::Result</code></a> with a <a href="struct.File.html"><code>File</code></a> inside that you can further
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operate on.</p>
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<h1 id='examples' class='section-header'><a href='#examples'>Examples</a></h1>
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<p>Opening a file to read:</p>
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<pre class='rust rust-example-rendered'>
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<span class='kw'>use</span> <span class='ident'>std</span>::<span class='ident'>fs</span>::<span class='ident'>OpenOptions</span>;
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<span class='kw'>let</span> <span class='ident'>file</span> <span class='op'>=</span> <span class='ident'>OpenOptions</span>::<span class='ident'>new</span>().<span class='ident'>read</span>(<span class='boolval'>true</span>).<span class='ident'>open</span>(<span class='string'>"foo.txt"</span>);</pre>
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<p>Opening a file for both reading and writing, as well as creating it if it
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doesn't exist:</p>
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<pre class='rust rust-example-rendered'>
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<span class='kw'>use</span> <span class='ident'>std</span>::<span class='ident'>fs</span>::<span class='ident'>OpenOptions</span>;
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<span class='kw'>let</span> <span class='ident'>file</span> <span class='op'>=</span> <span class='ident'>OpenOptions</span>::<span class='ident'>new</span>()
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.<span class='ident'>read</span>(<span class='boolval'>true</span>)
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.<span class='ident'>write</span>(<span class='boolval'>true</span>)
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.<span class='ident'>create</span>(<span class='boolval'>true</span>)
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.<span class='ident'>open</span>(<span class='string'>"foo.txt"</span>);</pre>
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</div><h2 id='methods'>Methods</h2><h3 class='impl'><code>impl <a class='struct' href='../../../bitflags/__core/fs/struct.OpenOptions.html' title='bitflags::__core::fs::OpenOptions'>OpenOptions</a></code></h3><div class='impl-items'><h4 id='method.new' class='method'><code>fn <a href='#method.new' class='fnname'>new</a>() -> <a class='struct' href='../../../bitflags/__core/fs/struct.OpenOptions.html' title='bitflags::__core::fs::OpenOptions'>OpenOptions</a></code></h4>
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<div class='docblock'><p>Creates a blank new set of options ready for configuration.</p>
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<p>All options are initially set to <code>false</code>.</p>
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<h1 id='examples-1' class='section-header'><a href='#examples-1'>Examples</a></h1>
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<pre class='rust rust-example-rendered'>
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<span class='kw'>use</span> <span class='ident'>std</span>::<span class='ident'>fs</span>::<span class='ident'>OpenOptions</span>;
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<span class='kw'>let</span> <span class='kw-2'>mut</span> <span class='ident'>options</span> <span class='op'>=</span> <span class='ident'>OpenOptions</span>::<span class='ident'>new</span>();
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<span class='kw'>let</span> <span class='ident'>file</span> <span class='op'>=</span> <span class='ident'>options</span>.<span class='ident'>read</span>(<span class='boolval'>true</span>).<span class='ident'>open</span>(<span class='string'>"foo.txt"</span>);</pre>
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</div><h4 id='method.read' class='method'><code>fn <a href='#method.read' class='fnname'>read</a>(&mut self, read: <a class='primitive' href='https://doc.rust-lang.org/nightly/bitflags/primitive.bool.html'>bool</a>) -> &mut <a class='struct' href='../../../bitflags/__core/fs/struct.OpenOptions.html' title='bitflags::__core::fs::OpenOptions'>OpenOptions</a></code></h4>
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<div class='docblock'><p>Sets the option for read access.</p>
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<p>This option, when true, will indicate that the file should be
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<code>read</code>-able if opened.</p>
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<h1 id='examples-2' class='section-header'><a href='#examples-2'>Examples</a></h1>
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<pre class='rust rust-example-rendered'>
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<span class='kw'>use</span> <span class='ident'>std</span>::<span class='ident'>fs</span>::<span class='ident'>OpenOptions</span>;
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<span class='kw'>let</span> <span class='ident'>file</span> <span class='op'>=</span> <span class='ident'>OpenOptions</span>::<span class='ident'>new</span>().<span class='ident'>read</span>(<span class='boolval'>true</span>).<span class='ident'>open</span>(<span class='string'>"foo.txt"</span>);</pre>
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</div><h4 id='method.write' class='method'><code>fn <a href='#method.write' class='fnname'>write</a>(&mut self, write: <a class='primitive' href='https://doc.rust-lang.org/nightly/bitflags/primitive.bool.html'>bool</a>) -> &mut <a class='struct' href='../../../bitflags/__core/fs/struct.OpenOptions.html' title='bitflags::__core::fs::OpenOptions'>OpenOptions</a></code></h4>
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<div class='docblock'><p>Sets the option for write access.</p>
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<p>This option, when true, will indicate that the file should be
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<code>write</code>-able if opened.</p>
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<p>If the file already exists, any write calls on it will overwrite its
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contents, without truncating it.</p>
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<h1 id='examples-3' class='section-header'><a href='#examples-3'>Examples</a></h1>
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<pre class='rust rust-example-rendered'>
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<span class='kw'>use</span> <span class='ident'>std</span>::<span class='ident'>fs</span>::<span class='ident'>OpenOptions</span>;
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<span class='kw'>let</span> <span class='ident'>file</span> <span class='op'>=</span> <span class='ident'>OpenOptions</span>::<span class='ident'>new</span>().<span class='ident'>write</span>(<span class='boolval'>true</span>).<span class='ident'>open</span>(<span class='string'>"foo.txt"</span>);</pre>
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</div><h4 id='method.append' class='method'><code>fn <a href='#method.append' class='fnname'>append</a>(&mut self, append: <a class='primitive' href='https://doc.rust-lang.org/nightly/bitflags/primitive.bool.html'>bool</a>) -> &mut <a class='struct' href='../../../bitflags/__core/fs/struct.OpenOptions.html' title='bitflags::__core::fs::OpenOptions'>OpenOptions</a></code></h4>
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<div class='docblock'><p>Sets the option for the append mode.</p>
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<p>This option, when true, means that writes will append to a file instead
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of overwriting previous contents.
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Note that setting <code>.write(true).append(true)</code> has the same effect as
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setting only <code>.append(true)</code>.</p>
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<p>For most filesystems, the operating system guarantees that all writes are
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atomic: no writes get mangled because another process writes at the same
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time.</p>
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<p>One maybe obvious note when using append-mode: make sure that all data
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that belongs together is written to the file in one operation. This
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can be done by concatenating strings before passing them to <code>write()</code>,
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or using a buffered writer (with a buffer of adequate size),
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and calling <code>flush()</code> when the message is complete.</p>
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<p>If a file is opened with both read and append access, beware that after
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opening, and after every write, the position for reading may be set at the
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end of the file. So, before writing, save the current position (using
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<code>seek(SeekFrom::Current(0))</code>, and restore it before the next read.</p>
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<h1 id='examples-4' class='section-header'><a href='#examples-4'>Examples</a></h1>
|
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<pre class='rust rust-example-rendered'>
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<span class='kw'>use</span> <span class='ident'>std</span>::<span class='ident'>fs</span>::<span class='ident'>OpenOptions</span>;
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<span class='kw'>let</span> <span class='ident'>file</span> <span class='op'>=</span> <span class='ident'>OpenOptions</span>::<span class='ident'>new</span>().<span class='ident'>append</span>(<span class='boolval'>true</span>).<span class='ident'>open</span>(<span class='string'>"foo.txt"</span>);</pre>
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</div><h4 id='method.truncate' class='method'><code>fn <a href='#method.truncate' class='fnname'>truncate</a>(&mut self, truncate: <a class='primitive' href='https://doc.rust-lang.org/nightly/bitflags/primitive.bool.html'>bool</a>) -> &mut <a class='struct' href='../../../bitflags/__core/fs/struct.OpenOptions.html' title='bitflags::__core::fs::OpenOptions'>OpenOptions</a></code></h4>
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<div class='docblock'><p>Sets the option for truncating a previous file.</p>
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<p>If a file is successfully opened with this option set it will truncate
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the file to 0 length if it already exists.</p>
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<p>The file must be opened with write access for truncate to work.</p>
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<h1 id='examples-5' class='section-header'><a href='#examples-5'>Examples</a></h1>
|
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<pre class='rust rust-example-rendered'>
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<span class='kw'>use</span> <span class='ident'>std</span>::<span class='ident'>fs</span>::<span class='ident'>OpenOptions</span>;
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|
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<span class='kw'>let</span> <span class='ident'>file</span> <span class='op'>=</span> <span class='ident'>OpenOptions</span>::<span class='ident'>new</span>().<span class='ident'>write</span>(<span class='boolval'>true</span>).<span class='ident'>truncate</span>(<span class='boolval'>true</span>).<span class='ident'>open</span>(<span class='string'>"foo.txt"</span>);</pre>
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</div><h4 id='method.create' class='method'><code>fn <a href='#method.create' class='fnname'>create</a>(&mut self, create: <a class='primitive' href='https://doc.rust-lang.org/nightly/bitflags/primitive.bool.html'>bool</a>) -> &mut <a class='struct' href='../../../bitflags/__core/fs/struct.OpenOptions.html' title='bitflags::__core::fs::OpenOptions'>OpenOptions</a></code></h4>
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<div class='docblock'><p>Sets the option for creating a new file.</p>
|
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|
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<p>This option indicates whether a new file will be created if the file
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does not yet already exist.</p>
|
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|
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<p>In order for the file to be created, <code>write</code> or <code>append</code> access must
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||
be used.</p>
|
||
|
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<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'>fs</span>::<span class='ident'>OpenOptions</span>;
|
||
|
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<span class='kw'>let</span> <span class='ident'>file</span> <span class='op'>=</span> <span class='ident'>OpenOptions</span>::<span class='ident'>new</span>().<span class='ident'>write</span>(<span class='boolval'>true</span>).<span class='ident'>create</span>(<span class='boolval'>true</span>).<span class='ident'>open</span>(<span class='string'>"foo.txt"</span>);</pre>
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</div><h4 id='method.create_new' class='method'><code>fn <a href='#method.create_new' class='fnname'>create_new</a>(&mut self, create_new: <a class='primitive' href='https://doc.rust-lang.org/nightly/bitflags/primitive.bool.html'>bool</a>) -> &mut <a class='struct' href='../../../bitflags/__core/fs/struct.OpenOptions.html' title='bitflags::__core::fs::OpenOptions'>OpenOptions</a></code><span class="since">1.9.0</span></h4>
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<div class='docblock'><p>Sets the option to always create a new file.</p>
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<p>This option indicates whether a new file will be created.
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No file is allowed to exist at the target location, also no (dangling)
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symlink.</p>
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<p>This option is useful because it as atomic. Otherwise between checking
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whether a file exists and creating a new one, the file may have been
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created by another process (a TOCTOU race condition / attack).</p>
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<p>If <code>.create_new(true)</code> is set, <code>.create()</code> and <code>.truncate()</code> are
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ignored.</p>
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<p>The file must be opened with write or append access in order to create
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a new file.</p>
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<h1 id='examples-7' class='section-header'><a href='#examples-7'>Examples</a></h1>
|
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<pre class='rust rust-example-rendered'>
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<span class='kw'>use</span> <span class='ident'>std</span>::<span class='ident'>fs</span>::<span class='ident'>OpenOptions</span>;
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<span class='kw'>let</span> <span class='ident'>file</span> <span class='op'>=</span> <span class='ident'>OpenOptions</span>::<span class='ident'>new</span>().<span class='ident'>write</span>(<span class='boolval'>true</span>)
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.<span class='ident'>create_new</span>(<span class='boolval'>true</span>)
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.<span class='ident'>open</span>(<span class='string'>"foo.txt"</span>);</pre>
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</div><h4 id='method.open' class='method'><code>fn <a href='#method.open' class='fnname'>open</a><P>(&self, path: P) -> <a class='enum' href='../../../bitflags/__core/result/enum.Result.html' title='bitflags::__core::result::Result'>Result</a><<a class='struct' href='../../../bitflags/__core/fs/struct.File.html' title='bitflags::__core::fs::File'>File</a>, <a class='struct' href='../../../bitflags/__core/io/struct.Error.html' title='bitflags::__core::io::Error'>Error</a>> <span class='where'>where P: <a class='trait' href='../../../bitflags/__core/convert/trait.AsRef.html' title='bitflags::__core::convert::AsRef'>AsRef</a><<a class='struct' href='../../../bitflags/__core/path/struct.Path.html' title='bitflags::__core::path::Path'>Path</a>></span></code></h4>
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<div class='docblock'><p>Opens a file at <code>path</code> with the options specified by <code>self</code>.</p>
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<h1 id='errors' class='section-header'><a href='#errors'>Errors</a></h1>
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<p>This function will return an error under a number of different
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circumstances, to include but not limited to:</p>
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<ul>
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<li>Opening a file that does not exist without setting <code>create</code> or
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<code>create_new</code>.</li>
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<li>Attempting to open a file with access that the user lacks
|
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permissions for</li>
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<li>Filesystem-level errors (full disk, etc)</li>
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<li>Invalid combinations of open options (truncate without write access,
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no access mode set, etc)</li>
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</ul>
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<h1 id='examples-8' class='section-header'><a href='#examples-8'>Examples</a></h1>
|
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<pre class='rust rust-example-rendered'>
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<span class='kw'>use</span> <span class='ident'>std</span>::<span class='ident'>fs</span>::<span class='ident'>OpenOptions</span>;
|
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|
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<span class='kw'>let</span> <span class='ident'>file</span> <span class='op'>=</span> <span class='ident'>OpenOptions</span>::<span class='ident'>new</span>().<span class='ident'>open</span>(<span class='string'>"foo.txt"</span>);</pre>
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</div></div><h2 id='implementations'>Trait Implementations</h2><h3 class='impl'><code>impl <a class='trait' href='../../../bitflags/__core/os/ext/prelude/trait.OpenOptionsExt.html' title='bitflags::__core::os::ext::prelude::OpenOptionsExt'>OpenOptionsExt</a> for <a class='struct' href='../../../bitflags/__core/fs/struct.OpenOptions.html' title='bitflags::__core::fs::OpenOptions'>OpenOptions</a></code><span class="since">1.1.0</span></h3><div class='impl-items'><h4 id='method.mode' class='method'><code>fn <a href='../../../bitflags/__core/os/ext/prelude/trait.OpenOptionsExt.html#tymethod.mode' class='fnname'>mode</a>(&mut self, mode: <a class='primitive' href='https://doc.rust-lang.org/nightly/bitflags/primitive.u32.html'>u32</a>) -> &mut <a class='struct' href='../../../bitflags/__core/fs/struct.OpenOptions.html' title='bitflags::__core::fs::OpenOptions'>OpenOptions</a></code></h4>
|
||
<h4 id='method.custom_flags' class='method'><code>fn <a href='../../../bitflags/__core/os/ext/prelude/trait.OpenOptionsExt.html#tymethod.custom_flags' class='fnname'>custom_flags</a>(&mut self, flags: <a class='primitive' href='https://doc.rust-lang.org/nightly/bitflags/primitive.i32.html'>i32</a>) -> &mut <a class='struct' href='../../../bitflags/__core/fs/struct.OpenOptions.html' title='bitflags::__core::fs::OpenOptions'>OpenOptions</a></code></h4>
|
||
</div><h3 id='derived_implementations'>Derived Implementations </h3><h3 class='impl'><code>impl <a class='trait' href='../../../bitflags/__core/clone/trait.Clone.html' title='bitflags::__core::clone::Clone'>Clone</a> for <a class='struct' href='../../../bitflags/__core/fs/struct.OpenOptions.html' title='bitflags::__core::fs::OpenOptions'>OpenOptions</a></code></h3><div class='impl-items'><h4 id='method.clone' class='method'><code>fn <a href='../../../bitflags/__core/clone/trait.Clone.html#tymethod.clone' class='fnname'>clone</a>(&self) -> <a class='struct' href='../../../bitflags/__core/fs/struct.OpenOptions.html' title='bitflags::__core::fs::OpenOptions'>OpenOptions</a></code></h4>
|
||
<h4 id='method.clone_from' class='method'><code>fn <a href='../../../bitflags/__core/clone/trait.Clone.html#method.clone_from' class='fnname'>clone_from</a>(&mut self, source: &Self)</code></h4>
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</div></section>
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Prefix searches with a type followed by a colon (e.g.
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