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
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
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 3.23 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/.
