1 .\" Copyright (c) 1980, 1991, 1993
2 .\" The Regents of the University of California. All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice, this list of conditions and the following disclaimer.
9 .\" 2. Redistributions in binary form must reproduce the above copyright
10 .\" notice, this list of conditions and the following disclaimer in the
11 .\" documentation and/or other materials provided with the distribution.
12 .\" 3. All advertising materials mentioning features or use of this software
13 .\" must display the following acknowledgement:
14 .\" This product includes software developed by the University of
15 .\" California, Berkeley and its contributors.
16 .\" 4. Neither the name of the University nor the names of its contributors
17 .\" may be used to endorse or promote products derived from this software
18 .\" without specific prior written permission.
20 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 .\" @(#)lseek.2 8.3 (Berkeley) 4/19/94
40 .Nd reposition read/write file offset
46 .Fn lseek "int fildes" "off_t offset" "int whence"
50 system call repositions the offset of the file descriptor
55 according to the directive
64 repositions the file position pointer associated with the file
68 .Bl -item -offset indent
82 the offset is set to its current location plus
90 the offset is set to the size of the
98 system call allows the file offset to be set beyond the end
99 of the existing end-of-file of the file.
100 If data is later written
101 at this point, subsequent reads of the data in the gap return
102 bytes of zeros (until data is actually written into the gap).
104 Some devices are incapable of seeking.
105 The value of the pointer
106 associated with such a device is undefined.
108 Upon successful completion,
110 returns the resulting offset location as measured in bytes from the
111 beginning of the file.
113 a value of -1 is returned and
121 will fail and the file position pointer will remain unchanged if:
127 is not an open file descriptor.
132 is not a proper value
133 or the resulting file offset would
134 be negative for a non-character special file.
136 The resulting file offset would be a value which cannot be represented
137 correctly in an object of type
143 is associated with a pipe, socket, or FIFO.
151 system call is expected to conform to
159 This document's use of
161 is incorrect English, but is maintained for historical reasons.