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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 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                             2004-12-11                        LSEEK64(3)