lseek
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NAME
lseek - reposition read/write file offset
SYNOPSIS
#include <unistd.h>
off_t lseek(int fildes, off_t offset, int whence);
DESCRIPTION
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 actu-
ally written into the gap).
Some devices are incapable of seeking. The value of the
pointer associated with such a device is undefined.
RETURN VALUES
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.
ERRORS
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.
CONFORMS TO
POSIX, BSD 4.3
BUGS
This document's use of whence is incorrect English, but
maintained for historical reasons.
SEE ALSO
dup(2), open(2), fseek(3)
Hurricane Electric Internet Services
Copyright (C) 1998
Hurricane Electric.
All Rights Reserved.