LSEEK(2) System Calls LSEEK(2)
lseek - reposition read/write file offset
off_t lseek (int fildes, off_t offset, int whence);
The lseek function repositions the offset of the file descriptor fildes
to the argument offset according to the directive whence. The argument
fildes must be an open file descriptor. Lseek repositions the file
pointer fildes as follows:
If whence is SEEK_SET, the offset is set to offset bytes. If
whence is SEEK_CUR, the offset is set to its current location
plus offset bytes. If whence is SEEK_END, the offset is set to
the size of the file plus offset bytes.
The lseek function allows the file offset to be set beyond the end of
the existing end-of-file of the file. If data is later written at this
point, subsequent reads of the data in the gap return bytes of zeros
(until data is actually written into the gap).
Some devices are incapable of seeking. The value of the pointer asso-
ciated with such a device is undefined.
Upon successful completion, lseek returns the resulting offset location
as measured in bytes from the beginning of the file. Otherwise, a
value of -1 is returned and errno is set to indicate the error.
Lseek will fail and the file pointer will remain unchanged if:
EBADF Fildes is not an open file descriptor.
ESPIPE Fildes is associated with a pipe, socket, or FIFO.
EINVAL Whence is not a proper value.
In the GNO implementation, doing an lseek past the end of file is per-
mitted, but the created gap (as mentioned above) is not gauranteed to
contain bytes of zeros.
This document's use of whence is incorrect English, but is maintained
for historical reasons.
The lseek function conforms to IEEE Std 1003.1-1988 (POSIX).
GNO 22 January 1997 LSEEK(2)
Man(1) output converted with