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| <h3 class="section">12.20 Stream Buffering</h3> |
| |
| <p><a name="index-buffering-of-streams-1131"></a>Characters that are written to a stream are normally accumulated and |
| transmitted asynchronously to the file in a block, instead of appearing |
| as soon as they are output by the application program. Similarly, |
| streams often retrieve input from the host environment in blocks rather |
| than on a character-by-character basis. This is called <dfn>buffering</dfn>. |
| |
| <p>If you are writing programs that do interactive input and output using |
| streams, you need to understand how buffering works when you design the |
| user interface to your program. Otherwise, you might find that output |
| (such as progress or prompt messages) doesn't appear when you intended |
| it to, or displays some other unexpected behavior. |
| |
| <p>This section deals only with controlling when characters are transmitted |
| between the stream and the file or device, and <em>not</em> with how |
| things like echoing, flow control, and the like are handled on specific |
| classes of devices. For information on common control operations on |
| terminal devices, see <a href="Low_002dLevel-Terminal-Interface.html#Low_002dLevel-Terminal-Interface">Low-Level Terminal Interface</a>. |
| |
| <p>You can bypass the stream buffering facilities altogether by using the |
| low-level input and output functions that operate on file descriptors |
| instead. See <a href="Low_002dLevel-I_002fO.html#Low_002dLevel-I_002fO">Low-Level I/O</a>. |
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| <li><a accesskey="1" href="Buffering-Concepts.html#Buffering-Concepts">Buffering Concepts</a>: Terminology is defined here. |
| <li><a accesskey="2" href="Flushing-Buffers.html#Flushing-Buffers">Flushing Buffers</a>: How to ensure that output buffers are flushed. |
| <li><a accesskey="3" href="Controlling-Buffering.html#Controlling-Buffering">Controlling Buffering</a>: How to specify what kind of buffering to use. |
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