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
       _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 in glibc and works without special defines.	 However,  the
       glibc  headers  do not provide a prototype.  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	compi-
       lation.

   _llseek()
       On 32-bit architectures, this is the system call that is used to imple-
       ment all of the above functions.	 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).

       64-bit systems don't need an _llseek() system call.  Instead, they have
       an lseek(2) system call that supports 64-bit file offsets.

ATTRIBUTES
       For   an	  explanation	of   the  terms	 used  in  this	 section,  see
       attributes(7).

       +----------+---------------+---------+
       |Interface | Attribute	  | Value   |
       +----------+---------------+---------+
       |lseek64() | Thread safety | MT-Safe |
       +----------+---------------+---------+
SEE ALSO
       llseek(2), lseek(2)

COLOPHON
       This page is part of release 4.10 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
       https://www.kernel.org/doc/man-pages/.



Linux				  2015-04-19			    LSEEK64(3)