<!-- Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009, 2013 The President and Fellows of Harvard College. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 3. Neither the name of the University nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. --> <html> <head> <title>getdirentry</title> <body bgcolor=#ffffff> <h2 align=center>getdirentry</h2> <h4 align=center>OS/161 Reference Manual</h4> <h3>Name</h3> <p> getdirentry - read filename from directory </p> <h3>Library</h3> <p> Standard C Library (libc, -lc) </p> <h3>Synopsis</h3> <p> <tt>#include <unistd.h></tt><br> <br> <tt>int</tt><br> <tt>getdirentry(int </tt><em>fd</em><tt>, char *</tt><em>buf</em><tt>, size_t </tt><em>buflen</em><tt>);</tt> </p> <h3>Description</h3> <p> <tt>getdirentry</tt> retrieves the next filename from a directory referred to by the file handle <em>filehandle</em>. The name is stored in <em>buf</em>, an area of size <em>buflen</em>. The length of of the name actually found is returned. </p> <p> Note: this call behaves like read() - the name stored in <em>buf</em> is not null-terminated. </p> <p> Which filename is the "next" is chosen based on the seek pointer associated with the file handle. The meaning of the seek pointer on a directory is defined by the filesystem in use and should not be interpreted - the only ways in which <A HREF=lseek.html>lseek</A> should be used are with SEEK_SET and an offset previously returned by lseek, or with any of SEEK_SET, SEEK_CUR, or SEEK_EOF with an offset of 0. </p> <p> <tt>getdirentry</tt> (like all system calls) should be atomic. In this case this means that each <tt>getdirentry</tt> call should return a name that was in the directory at the point in time when the call happened relative to other calls. <tt>getdirentry</tt> should never return names that have only been partially written or that have been partially erased. Note that the kernel is not obliged to (and generally cannot) make the getdirentry call atomic with respect to other threads in the same process accessing the transfer buffer during the operation. </p> <p> In general it is desirable for directory iteration to be stable; that is, opening a directory and reading it should yield a consistent snapshot of the directory state. Implementing this is a nuisance in general, and is worse in OS/161 since the system call we have can only return one name at a time. Therefore, it isn't required by default. (However, always check your course materials for the official word, just in case.) </p> <h3>Return Values</h3> <p> On success, <tt>getdirentry</tt> returns the length of the name transferred. On error, -1 is returned, and <A HREF=errno.html>errno</A> is set according to the error encountered. </p> <h3>Errors</h3> <table width=90%> <tr><td width=5% rowspan=4> </td> <td width=10% valign=top>EBADF</td> <td><em>fd</em> is not a valid file handle.</td></tr> <tr><td valign=top>ENOTDIR</td> <td><em>fd</em> does not refer to a directory.</td></tr> <tr><td valign=top>EIO</td> <td>A hard I/O error occurred.</td></tr> <tr><td valign=top>EFAULT</td> <td><em>buf</em> points to an invalid address.</td></tr> </table> </body> </html>