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
);
The library routine lseek
() 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).
llseek(2), lseek(2), feature_test_macros(7)
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