huschi.net

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 imple-
       mentation details, and for that reason these functions need not be sup-
       ported  on all POSIX-conforming systems. They are required on implemen-
       tations 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  some-
       times 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.1-2008, <dirent.h>, <sys_types.h>
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  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.unix.org/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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                          SEEKDIR(3P)