.\" Copyright (c) 1980 Regents of the University of California.
.\" All rights reserved. The Berkeley software License Agreement
.\" specifies the terms and conditions for redistribution.
.\" @(#)lseek.2 6.3 (Berkeley) 2/24/86
.TH LSEEK 2 "February 24, 1986"
lseek \- move read/write pointer
#define L_SET 0 /* set the seek pointer */
#define L_INCR 1 /* increment the seek pointer */
#define L_XTND 2 /* extend the file size */
pos = lseek(d, offset, whence)
refers to a file or device open for reading and/or writing.
is L_SET, the pointer is set to
is L_INCR, the pointer is set to its current location plus
is L_XTND, the pointer is set to the size of the
Upon successful completion, the resulting pointer location
as measured in bytes from beginning of the file is returned.
Some devices are incapable of seeking. The value of the pointer
associated with such a device is undefined.
Seeking far beyond the end of a file, then writing,
creates a gap or \*(lqhole\*(rq, which occupies no
physical space and reads as zeros.
Upon successful completion,
the current file pointer value is returned.
a value of \-1 is returned and \fIerrno\fP is set to indicate
will fail and the file pointer will remain unchanged if:
is not an open file descriptor.
is associated with a pipe or a socket.
is incorrect English, but maintained for historical reasons.