NAME
seekdir — set the
position of a directory stream
SYNOPSIS
void seekdir(DIR *dirp, long loc);
DESCRIPTION
The seekdir () function shall set the
position of the next readdir(3) 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(3). The new position reverts to the one associated
with the directory stream when telldir(3) was
performed.
If the value of loc was not obtained from an
earlier call to telldir(3), or if a call to
rewinddir(3) occurred between the call to
telldir(3) and the call to seekdir
(), the results of subsequent calls to readdir(3) are
unspecified.
RETURN VALUE
The seekdir () function shall not return a
value.
ERRORS
No errors are defined.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
The original standard developers perceived that there were
restrictions on the use of the seekdir () and
telldir(3) 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 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(3) 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(3) and later using rewinddir(3) and a loop on readdir(3) to relocate the position from which the filename was saved.
FUTURE DIRECTIONS
None.
SEE ALSO
opendir(3) , readdir(3) , telldir(3) , the Base Definitions volume of IEEE Std 1003.1-2001 (“POSIX.1”), <dirent.h>, <stdio.h>, <sys/types.h>
CHANGE HISTORY
First released in Issue 2.
Issue 6
In the SYNOPSIS, the inclusion of <sys/types.h> is no longer required.
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