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1 perry 1 FOPEN
2 !!!FOPEN
3 NAME
4 SYNOPSIS
5 DESCRIPTION
6 RETURN VALUE
7 ERRORS
8 CONFORMING TO
9 SEE ALSO
10 ----
11 !!NAME
12
13
14 fopen, fdopen, freopen - stream open functions
15 !!SYNOPSIS
16
17
18 __#include __
19
20
21 __FILE *fopen (const char *__''path''__, const char
22 *__''mode''__);
23 FILE *fdopen (int__ ''fildes''__, const char
24 *__''mode''__);
25 FILE *freopen (const char *__''path''__, const char
26 *__''mode''__, FILE
27 *__''stream''__);__
28 !!DESCRIPTION
29
30
31 The __fopen__ function opens the file whose name is the
32 string pointed to by ''path'' and associates a stream
33 with it.
34
35
36 The argument ''mode'' points to a string beginning with
37 one of the following sequences (Additional characters may
38 follow these sequences.):
39
40
41 __r__
42
43
44 Open text file for reading. The stream is positioned at the
45 beginning of the file.
46
47
48 __r+__
49
50
51 Open for reading and writing. The stream is positioned at
52 the beginning of the file.
53
54
55 __w__
56
57
58 Truncate file to zero length or create text file for
59 writing. The stream is positioned at the beginning of the
60 file.
61
62
63 __w+__
64
65
66 Open for reading and writing. The file is created if it does
67 not exist, otherwise it is truncated. The stream is
68 positioned at the beginning of the file.
69
70
71 __a__
72
73
74 Open for writing. The file is created if it does not exist.
75 The stream is positioned at the end of the
76 file.
77
78
79 __a+__
80
81
82 Open for reading and writing. The file is created if it does
83 not exist. The stream is positioned at the end of the
84 file.
85
86
87 The ''mode'' string can also include the letter ``b''
88 either as a last character or as a character between the
89 characters in any of the two-character strings described
90 above. This is strictly for compatibility with ANSI
91 X3.159-1989 (``ANSI C'') and has no effect; the ``b'' is
92 ignored on all POSIX conforming systems, including Linux.
93 (Other systems may treat text files and binary files
94 differently, and adding the ``b'' may be a good idea if you
95 do I/O to a binary file and expect that your program may be
96 ported to non-Unix environments.)
97
98
99 Any created files will have mode
100 __S_IRUSR__|__S_IWUSR__|__S_IRGRP__|__S_IWGRP__|__S_IROTH__|__S_IWOTH__
101 (0666), as modified by the process' umask value (see
102 umask(2).
103
104
105 Reads and writes may be intermixed on read/write streams in
106 any order. Note that ANSI C requires that a file positioning
107 function intervene between output and input, unless an input
108 operation encounters end-of-file. (If this condition is not
109 met, then a read is allowed to return the result of writes
110 other than the most recent.) Therefore it is good practice
111 (and indeed sometimes necessary under Linux) to put an
112 __fseek__ or __fgetpos__ operation between write and
113 read operations on such a stream. This operation may be an
114 apparent no-op (as in ''fseek(..., 0L, SEEK_CUR)'' called
115 for its synchronizing side effect.
116
117
118 The __fdopen__ function associates a stream with the
119 existing file descriptor, ''fildes''. The ''mode'' of
120 the stream (one of the values
121 ''fildes'', and the error and
122 end-of-file indicators are cleared. Modes
123 ''fdopen__ is closed. The result of applying
124 __fdopen__ to a shared memory object is
125 undefined.
126
127
128 The __freopen__ function opens the file whose name is the
129 string pointed to by ''path'' and associates the stream
130 pointed to by ''stream'' with it. The original stream (if
131 it exists) is closed. The ''mode'' argument is used just
132 as in the __fopen__ function. The primary use of the
133 __freopen__ function is to change the file associated
134 with a standard text stream (''stderr'', ''stdin'', or
135 ''stdout'').
136 !!RETURN VALUE
137
138
139 Upon successful completion __fopen__, __fdopen__ and
140 __freopen__ return a __FILE__ pointer. Otherwise,
141 __NULL__ is returned and the global variable ''errno''
142 is set to indicate the error.
143 !!ERRORS
144
145
146 __EINVAL__
147
148
149 The ''mode'' provided to __fopen__, __fdopen__, or
150 __freopen__ was invalid.
151
152
153 The __fopen__, __fdopen__ and __freopen__ functions
154 may also fail and set ''errno'' for any of the errors
155 specified for the routine malloc(3).
156
157
158 The __fopen__ function may also fail and set ''errno''
159 for any of the errors specified for the routine
160 open(2).
161
162
163 The __fdopen__ function may also fail and set
164 ''errno'' for any of the errors specified for the routine
165 fcntl(2).
166
167
168 The __freopen__ function may also fail and set
169 ''errno'' for any of the errors specified for the
170 routines open(2), fclose(3) and
171 fflush(3).
172 !!CONFORMING TO
173
174
175 The __fopen__ and __freopen__ functions conform to
176 ANSI X3.159-1989 (``ANSI C''). The __fdopen__ function
177 conforms to IEEE Std1003.1-1988 (``POSIX.1'').
178 !!SEE ALSO
179
180
181 open(2), fclose(3),
182 fileno(3)
183 ----
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