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| <h3 class="section">13.5 Dangers of Mixing Streams and Descriptors</h3> |
| |
| <p><a name="index-channels-1242"></a><a name="index-streams-and-descriptors-1243"></a><a name="index-descriptors-and-streams-1244"></a><a name="index-mixing-descriptors-and-streams-1245"></a> |
| You can have multiple file descriptors and streams (let's call both |
| streams and descriptors “channels” for short) connected to the same |
| file, but you must take care to avoid confusion between channels. There |
| are two cases to consider: <dfn>linked</dfn> channels that share a single |
| file position value, and <dfn>independent</dfn> channels that have their own |
| file positions. |
| |
| <p>It's best to use just one channel in your program for actual data |
| transfer to any given file, except when all the access is for input. |
| For example, if you open a pipe (something you can only do at the file |
| descriptor level), either do all I/O with the descriptor, or construct a |
| stream from the descriptor with <code>fdopen</code> and then do all I/O with |
| the stream. |
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| <ul class="menu"> |
| <li><a accesskey="1" href="Linked-Channels.html#Linked-Channels">Linked Channels</a>: Dealing with channels sharing a file position. |
| <li><a accesskey="2" href="Independent-Channels.html#Independent-Channels">Independent Channels</a>: Dealing with separately opened, unlinked channels. |
| <li><a accesskey="3" href="Cleaning-Streams.html#Cleaning-Streams">Cleaning Streams</a>: Cleaning a stream makes it safe to use |
| another channel. |
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