LSEEK64(3)                          Linux Programmer's Manual                          LSEEK64(3)



NAME
       lseek64 - reposition 64-bit read/write file offset

SYNOPSIS
       #define _LARGEFILE64_SOURCE     /* See feature_test_macros(7) */
       #include <sys/types.h>
       #include <unistd.h>

       off64_t lseek64(int fd, off64_t offset, int whence);

DESCRIPTION
       The  lseek(2)  family  of functions reposition the offset of the open file associated with
       the file descriptor fd to offset bytes relative to the start, current position, or end  of
       the file, when whence has the value SEEK_SET, SEEK_CUR, or SEEK_END, respectively.

       For more details, return value, and errors, see lseek(2).

       Four  interfaces  are  available:  lseek(2), lseek64(), llseek(2), and the raw system call
       _llseek(2).

   lseek
       Prototype:

           off_t lseek(int fd, off_t offset, int whence);

       lseek(2) uses the type off_t.  This is a  32-bit  signed  type  on  32-bit  architectures,
       unless one compiles with

           #define _FILE_OFFSET_BITS 64

       in which case it is a 64-bit signed type.

   lseek64
       Prototype:

           off64_t lseek64(int fd, off64_t offset, int whence);

       The  library  routine  lseek64() uses a 64-bit type even when off_t is a 32-bit type.  Its
       prototype (and the type off64_t) is available only when one compiles with

           #define _LARGEFILE64_SOURCE

       The function lseek64() is available since glibc 2.1, and is defined to  be  an  alias  for
       llseek().

   llseek
       Prototype:

           loff_t llseek(int fd, loff_t offset, int whence);

       The  type  loff_t  is a 64-bit signed type.  The library routine llseek() is available and
       glibc and works without special defines.  However, the glibc headers do not provide a pro‐
       totype.   Users  should  add  the  above  prototype, or something equivalent, to their own
       source.  When users complained about data loss caused by a  miscompilation  of  e2fsck(8),
       glibc 2.1.3 added the link-time warning

           "the `llseek´ function may be dangerous; use `lseek64´ instead."

       This makes this function unusable if one desires a warning-free compilation.

   _llseek
       All the above functions are implemented in terms of this system call.  The prototype is:

           int _llseek(int fd, off_t offset_hi, off_t offset_lo,
                       loff_t *result, int whence);

       For more details, see llseek(2).

ATTRIBUTES
   Multithreading (see pthreads(7))
       The lseek64() function is thread-safe.

SEE ALSO
       llseek(2), lseek(2)

COLOPHON
       This  page  is  part of release 3.74 of the Linux man-pages project.  A description of the
       project, information about reporting bugs, and the latest version of  this  page,  can  be
       found at http://www.kernel.org/doc/man-pages/.



Linux                                       2014-08-19                                 LSEEK64(3)