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<title>Input/output streams</title>
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<h2 class="title">Input/output streams</h2>
<p class="para">
The <acronym title="Command Line Interpreter/Interface">CLI</acronym> <acronym title="Server Application Programming Interface">SAPI</acronym> defines a few constants for I/O streams to make programming
for the command line a bit easier.
</p>
<p class="para">
<table class="doctable table">
<caption><strong>CLI specific Constants</strong></caption>
<thead>
<tr>
<th>Constant</th>
<th>Description</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td><strong><code>STDIN</code></strong></td>
<td>
<p class="para">An already opened stream to <em>stdin</em>. This saves
opening it with
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$stdin </span><span style="color: #007700">= </span><span style="color: #0000BB">fopen</span><span style="color: #007700">(</span><span style="color: #DD0000">'php://stdin'</span><span style="color: #007700">, </span><span style="color: #DD0000">'r'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
If you want to read single line from <em>stdin</em>, you can
use
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$line </span><span style="color: #007700">= </span><span style="color: #0000BB">trim</span><span style="color: #007700">(</span><span style="color: #0000BB">fgets</span><span style="color: #007700">(</span><span style="color: #0000BB">STDIN</span><span style="color: #007700">)); </span><span style="color: #FF8000">// reads one line from STDIN<br /></span><span style="color: #0000BB">fscanf</span><span style="color: #007700">(</span><span style="color: #0000BB">STDIN</span><span style="color: #007700">, </span><span style="color: #DD0000">"%d\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">$number</span><span style="color: #007700">); </span><span style="color: #FF8000">// reads number from STDIN<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</p></td>
</tr>
<tr>
<td><strong><code>STDOUT</code></strong></td>
<td><p class="para">
An already opened stream to <em>stdout</em>. This saves
opening it with
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$stdout </span><span style="color: #007700">= </span><span style="color: #0000BB">fopen</span><span style="color: #007700">(</span><span style="color: #DD0000">'php://stdout'</span><span style="color: #007700">, </span><span style="color: #DD0000">'w'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</p></td>
</tr>
<tr>
<td><strong><code>STDERR</code></strong></td>
<td>
<p class="para">
An already opened stream to <em>stderr</em>.
This saves opening it with
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$stderr </span><span style="color: #007700">= </span><span style="color: #0000BB">fopen</span><span style="color: #007700">(</span><span style="color: #DD0000">'php://stderr'</span><span style="color: #007700">, </span><span style="color: #DD0000">'w'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</p>
</td>
</tr>
</tbody>
</table>
</p>
<p class="para">
Given the above, you don't need to open e.g. a stream for
<em>stderr</em> yourself but simply use the constant instead of
the stream resource:
<div class="example-contents">
<div class="shellcode"><pre class="shellcode">php -r 'fwrite(STDERR, "stderr\n");'</pre>
</div>
</div>
You do not need to explicitly close these streams, as they are closed
automatically by PHP when your script ends.
</p>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
These constants are not available if reading the PHP script from
<em>stdin</em>.
</p>
</p></blockquote>
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