LSEEK(2) | System Calls Manual | LSEEK(2) |
lseek
, seek
—
#include <unistd.h>
off_t
lseek
(int
fildes, off_t
offset, int
whence);
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:
SEEK_SET
, the
offset is set to offset bytes.SEEK_CUR
, the
offset is set to its current location plus offset
bytes.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 associated with such a device is undefined.
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:
lseek
() function conforms to IEEE
Std 1003.1-1990 (“POSIX.1”).
seek
() function appeared in
Version 1 AT&T UNIX, later renamed into
lseek
() for “long seek” due to a larger
offset argument type.
September 2, 2019 | NetBSD 9.0 |