lseek64 - reposition 64-bit read/write file offset
#define _LARGEFILE64_SOURCE /* See feature_test_macros(7) */
The lseek(2) family of functions reposition the offset of the open file associated with the file descriptor
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).
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.
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
loff_t llseek(int fd, loff_t offset, int whence);
loff_t is 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.
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).
This page is part of release 4.15 of the Linux
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