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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&mdash;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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