Programming

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



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

SYNOPSIS
       #define _LARGEFILE64_SOURCE
       #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 in libc5 and glibc and works without special defines.  Its
       prototype  was  given in <unistd.h> with libc5, but glibc does not pro-
       vide a prototype.  This is bad, since a  prototype  is  needed.   Users
       should  add  the above prototype, or something equivalent, to their own
       source.  When users complained about data loss caused by a  miscompila-
       tion 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
       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).

SEE ALSO
       llseek(2), lseek(2), feature_test_macros(7)

COLOPHON
       This  page  is  part of release 3.18 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.



Linux                             2004-12-11                        LSEEK64(3)