lseek
OS/161 Reference Manual
Name
lseek - change current position in file
Library
Standard C Library (libc, -lc)
Synopsis
#include <unistd.h>
off_t
lseek(int fd, off_t pos, int whence);
Description
lseek alters the current seek position of the file handle
filehandle, seeking to a new position based on pos
and whence.
If whence is
- SEEK_SET, the new position is pos.
- SEEK_CUR, the new position is the current position plus pos.
- SEEK_END, the new position is the position of end-of-file
plus pos.
- anything else, lseek fails.
Note that pos is a signed quantity.
It is not meaningful to seek on certain objects (such as the console
device). All seeks on these objects fail.
Seek positions less than zero are invalid. Seek positions beyond EOF
are legal.
Note that each distinct open of a file should have an independent seek
pointer.
Return Values
On success, lseek returns the new position. On error, -1 is returned,
and errno is set according to the error
encountered.
Errors
The following error codes should be returned under the conditions
given. Other error codes may be returned for other errors not
mentioned here.
| | |
| EBADF | fd is not a valid file handle. |
| ESPIPE | fd refers to an object which does
not support seeking. |
| EINVAL | whence is invalid. |
| EINVAL | The resulting seek position would be negative. |