126 lines
4.5 KiB
HTML
126 lines
4.5 KiB
HTML
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<html>
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<head>
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<title>getdirentry</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>getdirentry</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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getdirentry - read filename from directory
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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>getdirentry(int </tt><em>fd</em><tt>, char *</tt><em>buf</em><tt>,
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size_t </tt><em>buflen</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>getdirentry</tt> retrieves the next filename from a directory
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referred to by the file handle <em>filehandle</em>. The name is stored
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in <em>buf</em>, an area of size <em>buflen</em>. The length of of the
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name actually found is returned.
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</p>
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<p>
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Note: this call behaves like read() - the name stored in <em>buf</em>
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is not null-terminated.
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</p>
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<p>
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Which filename is the "next" is chosen based on the seek pointer
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associated with the file handle. The meaning of the seek pointer on a
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directory is defined by the filesystem in use and should not be
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interpreted - the only ways in which <A HREF=lseek.html>lseek</A>
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should be used are with SEEK_SET and an offset previously returned by
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lseek, or with any of SEEK_SET, SEEK_CUR, or SEEK_EOF with an offset
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of 0.
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</p>
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<p>
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<tt>getdirentry</tt> (like all system calls) should be atomic. In this
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case this means that each <tt>getdirentry</tt> call should return a
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name that was in the directory at the point in time when the call
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happened relative to other calls. <tt>getdirentry</tt> should never
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return names that have only been partially written or that have been
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partially erased.
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Note that the kernel is not obliged to (and generally cannot) make the
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getdirentry call atomic with respect to other threads in the same
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process accessing the transfer buffer during the operation.
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</p>
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<p>
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In general it is desirable for directory iteration to be stable; that
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is, opening a directory and reading it should yield a consistent
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snapshot of the directory state. Implementing this is a nuisance in
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general, and is worse in OS/161 since the system call we have can only
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return one name at a time. Therefore, it isn't required by default.
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(However, always check your course materials for the official word,
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just in case.)
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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>getdirentry</tt> returns the length of the name
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transferred. On error, -1 is returned, and
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<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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<table width=90%>
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<tr><td width=5% rowspan=4> </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
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handle.</td></tr>
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<tr><td valign=top>ENOTDIR</td> <td><em>fd</em> does not refer to a
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directory.</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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</body>
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</html>
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