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I/O Constructors [C++ Reference]
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<h2><a name="io_constructors" id="io_constructors">I/O Constructors</a></h2>
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<p>
Syntax:
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<pre class="c code c++" style="font-family:monospace;"> <span class="co2">#include <fstream></span>
fstream<span class="br0">(</span> <span class="kw4">const</span> <span class="kw4">char</span> <span class="sy0">*</span>filename<span class="sy0">,</span> ios_base<span class="sy0">::</span><span class="me2">openmode</span> mode <span class="br0">)</span><span class="sy0">;</span>
ifstream<span class="br0">(</span> <span class="kw4">const</span> <span class="kw4">char</span> <span class="sy0">*</span>filename<span class="sy0">,</span> ios_base<span class="sy0">::</span><span class="me2">openmode</span> mode <span class="br0">)</span><span class="sy0">;</span>
ofstream<span class="br0">(</span> <span class="kw4">const</span> <span class="kw4">char</span> <span class="sy0">*</span>filename<span class="sy0">,</span> ios_base<span class="sy0">::</span><span class="me2">openmode</span> mode <span class="br0">)</span><span class="sy0">;</span></pre>
<p>
The fstream, ifstream, and ofstream objects are used to do file I/O. The
optional mode defines how the file is to be opened, according to the <a href="../io/io_flags#mode_flags.html" class="wikilink1" title="io:io_flags">IO stream
mode flags</a>. The optional filename specifies the file to be opened and
associated with the stream.
</p>
<p>
Input and output file streams can be used in a similar manner to C++ predefined
I/O streams, cin and cout.
</p>
<p>
For example, the following code reads input data and appends the result to an output file.
</p>
<pre class="c code c++" style="font-family:monospace;"> ifstream fin<span class="br0">(</span> <span class="st0">"/tmp/data.txt"</span> <span class="br0">)</span><span class="sy0">;</span>
ofstream fout<span class="br0">(</span> <span class="st0">"/tmp/results.txt"</span><span class="sy0">,</span> ios_base<span class="sy0">::</span><span class="me2">app</span> <span class="br0">)</span><span class="sy0">;</span>
<span class="kw1">while</span> <span class="br0">(</span> fin <span class="sy0">>></span> temp <span class="br0">)</span>
fout <span class="sy0"><<</span> temp <span class="sy0">+</span> 2 <span class="sy0"><<</span> endl<span class="sy0">;</span>
<span class="co1">// Files are closed automatically when the variables fin and fout fall out of scope.</span></pre>
<p>
Related Topics: <a href="../io/close.html" class="wikilink1" title="io:close">close</a>, <a href="../io/open.html" class="wikilink1" title="io:open">open</a>
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