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 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).

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

COLOPHON
       This  page  is  part of release 3.25 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)