lseek64 — reposition 64-bit read/write file offset
#define _LARGEFILE64_SOURCE #include <sys/types.h> #include <unistd.h>
off64_t lseek64( |
int | fd, |
| off64_t | offset, | |
| int | whence); |
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).
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.
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().
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.
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).
This page is part of release 2.79 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/.
|
Copyright 2004 Andries Brouwer <aebcwi.nl>. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. |