SEEKDIR(3P)                                         POSIX Programmer's Manual                                        SEEKDIR(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       seekdir - set the position of a directory stream

SYNOPSIS
       #include <dirent.h>

       void seekdir(DIR *dirp, long loc);


DESCRIPTION
       The  seekdir()  function shall set the position of the next readdir() operation on the directory stream specified by dirp
       to the position specified by loc. The value of loc should have been returned from an earlier call to telldir().  The  new
       position reverts to the one associated with the directory stream when telldir() was performed.

       If  the value of loc was not obtained from an earlier call to telldir(), or if a call to rewinddir() occurred between the
       call to telldir() and the call to seekdir(), the results of subsequent calls to readdir() are unspecified.

RETURN VALUE
       The seekdir() function shall not return a value.

ERRORS
       No errors are defined.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       None.

RATIONALE
       The original standard developers perceived that there were restrictions on the use of the seekdir() and  telldir()  func-
       tions  related to implementation details, and for that reason these functions need not be supported on all POSIX-conform-
       ing systems. They are required on implementations supporting the XSI extension.

       One of the perceived problems of implementation is that returning to a given point in a directory is quite  difficult  to
       describe  formally,  in spite of its intuitive appeal, when systems that use B-trees, hashing functions, or other similar
       mechanisms to order their directories are considered. The definition of seekdir() and telldir() does not specify whether,
       when using these interfaces, a given directory entry will be seen at all, or more than once.

       On  systems  not supporting these functions, their capability can sometimes be accomplished by saving a filename found by
       readdir() and later using rewinddir() and a loop on readdir() to relocate the position from which the filename was saved.

FUTURE DIRECTIONS
       None.

SEE ALSO
       opendir(),  readdir(),  telldir(),  the  Base  Definitions  volume  of   IEEE Std 1003.1-2001,   <dirent.h>,   <stdio.h>,
       <sys/types.h>

COPYRIGHT
       Portions  of  this  text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for
       Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6,  Copy-
       right (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any
       discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open  Group
       Standard   is   the   referee   document.   The   original   Standard   can   be   obtained  online  at  http://www.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                   SEEKDIR(3P)