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| <h4 class="subsection">12.20.1 Buffering Concepts</h4> |
| |
| <p>There are three different kinds of buffering strategies: |
| |
| <ul> |
| <li>Characters written to or read from an <dfn>unbuffered</dfn> stream are |
| transmitted individually to or from the file as soon as possible. |
| <a name="index-unbuffered-stream-1132"></a> |
| <li>Characters written to a <dfn>line buffered</dfn> stream are transmitted to |
| the file in blocks when a newline character is encountered. |
| <a name="index-line-buffered-stream-1133"></a> |
| <li>Characters written to or read from a <dfn>fully buffered</dfn> stream are |
| transmitted to or from the file in blocks of arbitrary size. |
| <a name="index-fully-buffered-stream-1134"></a></ul> |
| |
| <p>Newly opened streams are normally fully buffered, with one exception: a |
| stream connected to an interactive device such as a terminal is |
| initially line buffered. See <a href="Controlling-Buffering.html#Controlling-Buffering">Controlling Buffering</a>, for information |
| on how to select a different kind of buffering. Usually the automatic |
| selection gives you the most convenient kind of buffering for the file |
| or device you open. |
| |
| <p>The use of line buffering for interactive devices implies that output |
| messages ending in a newline will appear immediately—which is usually |
| what you want. Output that doesn't end in a newline might or might not |
| show up immediately, so if you want them to appear immediately, you |
| should flush buffered output explicitly with <code>fflush</code>, as described |
| in <a href="Flushing-Buffers.html#Flushing-Buffers">Flushing Buffers</a>. |
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