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 in libc5 and glibc
       and works without special defines.  Its prototype was given in <unistd.h> with libc5, but glibc does  not
       provide 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
       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 3.54 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                                              2013-08-19                                         LSEEK64(3)