1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
|
.\" Copyright (c) 1990, 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek and the American National Standards Committee X3,
.\" on Information Processing Systems.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\" must display the following acknowledgement:
.\" This product includes software developed by the University of
.\" California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" @(#)fseek.3 6.11 (Berkeley) 6/29/91
.\"
.\" Converted for Linux, Mon Nov 29 15:22:01 1993, faith@cs.unc.edu
.\"
.TH FSEEK 3 1993-11-29 "BSD MANPAGE" "Linux Programmer's Manual"
.SH NAME
fgetpos, fseek, fsetpos, ftell, rewind \- reposition a stream
.SH SYNOPSIS
.B #include <stdio.h>
.sp
.BI "int fseek(FILE *" stream ", long " offset ", int " whence );
.br
.BI "long ftell(FILE *" stream );
.br
.BI "void rewind(FILE *" stream );
.br
.BI "int fgetpos(FILE *" stream ", fpos_t *" pos );
.br
.BI "int fsetpos(FILE *" stream ", fpos_t *" pos );
.SH DESCRIPTION
The
.B fseek
function sets the file position indicator for the stream pointed to by
.IR stream .
The new position, measured in bytes, is obtained by adding
.I offset
bytes to the position specified by
.IR whence .
If
.I whence
is set to
.BR SEEK_SET ,
.BR SEEK_CUR ,
or
.BR SEEK_END ,
the offset is relative to the start of the file, the current position
indicator, or end-of-file, respectively. A successful call to the
.B fseek
function clears the end-of-file indicator for the stream and undoes
any effects of the
.BR ungetc (3)
function on the same stream.
.PP
The
.B ftell
function obtains the current value of the file position indicator for the
stream pointed to by
.IR stream .
.PP
The
.B rewind
function sets the file position indicator for the stream pointed to by
.I stream
to the beginning of the file. It is equivalent to:
.PP
.RS
(void)fseek(stream, 0L, SEEK_SET)
.RE
.PP
except that the error indicator for the stream is also cleared (see
.BR clearerr (3)).
.PP
The
.B fgetpos
and
.B fsetpos
functions are alternate interfaces equivalent to
.B ftell
and
.B fseek
(with whence set to
.BR SEEK_SET ),
setting and storing the current value of the file offset into or from the
object referenced by
.IR pos .
On some non-UNIX systems an
.B fpos_t
object may be a complex object and these routines may be the only way to
portably reposition a text stream.
.SH "RETURN VALUE"
The
.B rewind
function returns no value. Upon successful completion,
.BR fgetpos ,
.BR fseek ,
.B fsetpos
return 0,
and
.B ftell
returns the current offset. Otherwise, \-1 is returned and the global
variable errno is set to indicate the error.
.SH ERRORS
.TP
.B EBADF
The
.I stream
specified is not a seekable stream.
.TP
.B EINVAL
The
.I whence
argument to
.B fseek
was not
.BR SEEK_SET ,
.BR SEEK_END ,
or
.BR SEEK_CUR .
.PP
The function
.BR fgetpos ,
.BR fseek ,
.BR fsetpos ,
and
.B ftell
may also fail and set
.I errno
for any of the errors specified for the routines
.BR fflush (3),
.BR fstat (2),
.BR lseek (2),
and
.BR malloc (3).
.SH "CONFORMING TO"
The
.BR fgetpos ,
.BR fsetpos ,
.BR fseek ,
.BR ftell ,
and
.BR rewind
functions conform to ANSI X3.159-1989 (``ANSI C'').
.SH "SEE ALSO"
.BR lseek (2),
.BR fseeko (3)
|
