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



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

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() using the same directory stream. 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() functions related to
       implementation details, and for that reason these functions need not be
       supported on all POSIX-conforming systems. They are required on
       implementations supporting the XSI option.

       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
       fdopendir(), readdir(), telldir()

       The Base Definitions volume of POSIX.1-2017, <dirent.h>, <sys_types.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                           SEEKDIR(3)
