Manpage of LSEEK64

LSEEK64

Section: Linux Programmer's Manual (3)
Updated: 2015-04-19
Index
 

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 fdto offsetbytes relative to the start, current position, or end of the file, when whencehas 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 _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_tis 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_tis a 64-bit signed type. The library routine llseek() is available in glibc and works without special defines. However, the glibc headers do not provide a prototype. 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()

On 32-bit architectures, this is the system call that is used to implement all of the above functions. 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).

64-bit systems don't need an _llseek() system call. Instead, they have an lseek(2) system call that supports 64-bit file offsets.  

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).
InterfaceAttributeValue
lseek64() Thread safetyMT-Safe
 

SEE ALSO

llseek(2), lseek(2)


 

Index

NAME
SYNOPSIS
DESCRIPTION
lseek()
lseek64()
llseek()
_llseek()
ATTRIBUTES
SEE ALSO

This document was created by man2html, using the manual pages.
Time: 16:30:25 GMT, December 12, 2016 Click Here!