Section: POSIX Programmer's Manual (3P)
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.
--- set the position of a directory stream
void seekdir(DIR *dirp, long loc);
function shall set the position of the next
operation on the directory stream specified by
to the position specified by
The value of
should have been returned from an earlier call to
using the same directory stream. The new position reverts to the one
associated with the directory stream when
If the value of
was not obtained from an earlier call to
or if a call to
occurred between the call to
and the call to
the results of subsequent calls to
function shall not return a value.
No errors are defined.
The following sections are informative.
The original standard developers perceived that there were restrictions
on the use of the
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
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
and later using
and a loop on
to relocate the position from which the filename was saved.
The Base Definitions volume of POSIX.1-2017,
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
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