seekdir(3p) — Linux manual page

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 (consult 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() 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(3p), readdir(3p), telldir(3p)

       The Base Definitions volume of POSIX.1‐2017, dirent.h(0p),
       sys_types.h(0p)

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(3P)

Pages that refer to this page: dirent.h(0p), telldir(3p)

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