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<a name="EOF-and-Errors"></a>
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<p>
Next: <a href="File-Positioning.html#File-Positioning" accesskey="n" rel="next">File Positioning</a>, Previous: <a href="Temporary-Files.html#Temporary-Files" accesskey="p" rel="prev">Temporary Files</a>, Up: <a href="C_002dStyle-I_002fO-Functions.html#C_002dStyle-I_002fO-Functions" accesskey="u" rel="up">C-Style I/O Functions</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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<a name="End-of-File-and-Errors"></a>
<h4 class="subsection">14.2.18 End of File and Errors</h4>
<p>Once a file has been opened its status can be acquired. As an example
the <code>feof</code> functions determines if the end of the file has been
reached. This can be very useful when reading small parts of a file
at a time. The following example shows how to read one line at a time
from a file until the end has been reached.
</p>
<div class="example">
<pre class="example">filename = "myfile.txt";
fid = fopen (filename, "r");
while (! feof (fid) )
text_line = fgetl (fid);
endwhile
fclose (fid);
</pre></div>
<p>Note that in some situations it is more efficient to read the entire
contents of a file and then process it, than it is to read it line by
line. This has the potential advantage of removing the loop in the
above code.
</p>
<a name="XREFfeof"></a><dl>
<dt><a name="index-feof"></a>Built-in Function: <em></em> <strong>feof</strong> <em>(<var>fid</var>)</em></dt>
<dd><p>Return 1 if an end-of-file condition has been encountered for a given
file and 0 otherwise. Note that it will only return 1 if the end of the
file has already been encountered, not if the next read operation will
result in an end-of-file condition.
</p>
<p><strong>See also:</strong> <a href="Binary-I_002fO.html#XREFfread">fread</a>, <a href="Opening-and-Closing-Files.html#XREFfopen">fopen</a>.
</p></dd></dl>
<a name="XREFferror"></a><dl>
<dt><a name="index-ferror"></a>Built-in Function: <em>[<var>err</var>, <var>msg</var>] =</em> <strong>ferror</strong> <em>(<var>fid</var>)</em></dt>
<dt><a name="index-ferror-1"></a>Built-in Function: <em>[<var>err</var>, <var>msg</var>] =</em> <strong>ferror</strong> <em>(<var>fid</var>, "clear")</em></dt>
<dd><p>Return 1 if an error condition has been encountered for the file ID
<var>fid</var> and 0 otherwise. Note that it will only return 1 if an error
has already been encountered, not if the next operation will result in
an error condition.
</p>
<p>The second argument is optional. If it is supplied, also clear the
error condition.
</p>
<p><strong>See also:</strong> <a href="#XREFfclear">fclear</a>, <a href="Opening-and-Closing-Files.html#XREFfopen">fopen</a>.
</p></dd></dl>
<a name="XREFfclear"></a><dl>
<dt><a name="index-fclear"></a>Built-in Function: <em></em> <strong>fclear</strong> <em>(<var>fid</var>)</em></dt>
<dd><p>Clear the stream state for the specified file.
</p>
<p><strong>See also:</strong> <a href="Opening-and-Closing-Files.html#XREFfopen">fopen</a>.
</p></dd></dl>
<a name="XREFfreport"></a><dl>
<dt><a name="index-freport"></a>Built-in Function: <em></em> <strong>freport</strong> <em>()</em></dt>
<dd><p>Print a list of which files have been opened, and whether they are open
for reading, writing, or both. For example:
</p>
<div class="example">
<pre class="example">freport ()
-| number mode name
-|
-| 0 r stdin
-| 1 w stdout
-| 2 w stderr
-| 3 r myfile
</pre></div>
<p><strong>See also:</strong> <a href="Opening-and-Closing-Files.html#XREFfopen">fopen</a>, <a href="Opening-and-Closing-Files.html#XREFfclose">fclose</a>.
</p></dd></dl>
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