100 lines
3.2 KiB
HTML
100 lines
3.2 KiB
HTML
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The President and Fellows of Harvard College.
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-->
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<html>
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<head>
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<title>ftruncate</title>
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<link rel="stylesheet" type="text/css" media="all" href="../man.css">
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</head>
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<body bgcolor=#ffffff>
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<h2 align=center>ftruncate</h2>
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<h4 align=center>OS/161 Reference Manual</h4>
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<h3>Name</h3>
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<p>
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ftruncate - set size of a file
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</p>
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<h3>Library</h3>
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<p>
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Standard C Library (libc, -lc)
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</p>
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<h3>Synopsis</h3>
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<p>
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<tt>#include <unistd.h></tt><br>
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<br>
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<tt>int</tt><br>
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<tt>ftruncate(int </tt><em>fd</em><tt>, off_t </tt><em>filesize</em><tt>);</tt>
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</p>
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<h3>Description</h3>
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<p>
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<tt>ftruncate</tt> forcibly sets the size of the file referred to by
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<em>fd</em> to <em>filesize</em>. If this expands the file, the new
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data appears as if it is zero-filled. (On file systems that support
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sparse files, the new space does not need to be physically allocated.)
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If the action shrinks the file, the excess data is discarded.
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</p>
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<p>
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The file must be open for write.
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</p>
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<p>
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<tt>ftruncate</tt> must be atomic. For recoverable file systems, this
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includes after crashing and running recovery.
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</p>
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<h3>Return Values</h3>
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<p>
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On success, <tt>ftruncate</tt> returns 0. On error, -1 is returned,
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and <A HREF=errno.html>errno</A> is set according to the error
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encountered.
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</p>
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<h3>Errors</h3>
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<p>
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The following error codes should be returned under the conditions
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given. Other error codes may be returned for other cases not
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mentioned here.
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<table width=90%>
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<tr><td width=5% rowspan=3> </td>
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<td width=10% valign=top>EBADF</td>
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<td><em>fd</em> is not a valid file handle, or
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it is not open for writing.</td></tr>
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<tr><td valign=top>EIO</td> <td>A hard I/O error occurred.</td></tr>
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<tr><td valign=top>EFAULT</td> <td><em>buf</em> points to an invalid
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address.</td></tr>
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</table>
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</p>
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</body>
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</html>
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