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open [C++ Reference]
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<h2><a name="open" id="open">open</a></h2>
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<p>
Syntax:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="co2">#include <fstream></span>
<span class="kw4">void</span> fstream<span class="sy0">::</span><span class="me2">open</span><span class="br0">(</span><span class="kw4">const</span> <span class="kw4">char</span> <span class="sy0">*</span>filename<span class="sy0">,</span> openmode mode <span class="sy0">=</span> default_mode<span class="br0">)</span><span class="sy0">;</span></pre>
<p>
The function open() is used with file streams. It opens filename and associates
it with the current stream. The mode parameter defaults to
ios::in for ifstream, ios::out for ofstream, and ios::in|ios::out for fstream.
If open() fails, the stream is put into a non-good state which may be checked. For example:
</p>
<pre class="c code c++" style="font-family:monospace;"> ifstream inputStream<span class="sy0">;</span>
inputStream.<span class="me1">open</span><span class="br0">(</span><span class="st0">"file.txt"</span><span class="br0">)</span><span class="sy0">;</span>
<span class="kw1">if</span><span class="br0">(</span> <span class="sy0">!</span>inputStream <span class="br0">)</span> <span class="br0">{</span>
cerr <span class="sy0"><<</span> <span class="st0">"Error opening input stream"</span> <span class="sy0"><<</span> endl<span class="sy0">;</span>
<span class="br0">}</span>
<span class="co1">// or</span>
<span class="kw1">if</span> <span class="br0">(</span> inputStream <span class="br0">)</span> <span class="br0">{</span>
<span class="co1">// use inputStream</span>
<span class="br0">}</span></pre>
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Related Topics: <a href="../io/constructors.html" class="wikilink1" title="io:constructors">I/O Constructors</a>, <a href="../io/close.html" class="wikilink1" title="io:close">close</a>, <a href="../io/io_flags#mode_flags.html" class="wikilink1" title="io:io_flags">C++ I/O Mode Flags</a>
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