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1=pod
2
3=head1 NAME
4
5BIO_s_file, BIO_new_file, BIO_new_fp, BIO_set_fp, BIO_get_fp,
6BIO_read_filename, BIO_write_filename, BIO_append_filename,
7BIO_rw_filename - FILE bio
8
9=head1 SYNOPSIS
10
11 #include <openssl/bio.h>
12
13 const BIO_METHOD *BIO_s_file(void);
14 BIO *BIO_new_file(const char *filename, const char *mode);
15 BIO *BIO_new_fp(FILE *stream, int flags);
16
17 BIO_set_fp(BIO *b, FILE *fp, int flags);
18 BIO_get_fp(BIO *b, FILE **fpp);
19
20 int BIO_read_filename(BIO *b, char *name);
21 int BIO_write_filename(BIO *b, char *name);
22 int BIO_append_filename(BIO *b, char *name);
23 int BIO_rw_filename(BIO *b, char *name);
24
25=head1 DESCRIPTION
26
27BIO_s_file() returns the BIO file method. As its name implies it
28is a wrapper round the stdio FILE structure and it is a
29source/sink BIO.
30
31Calls to BIO_read_ex() and BIO_write_ex() read and write data to the
32underlying stream. BIO_gets() and BIO_puts() are supported on file BIOs.
33
34BIO_flush() on a file BIO calls the fflush() function on the wrapped
35stream.
36
37BIO_reset() attempts to change the file pointer to the start of file
38using fseek(stream, 0, 0).
39
40BIO_seek() sets the file pointer to position B<ofs> from start of file
41using fseek(stream, ofs, 0).
42
43BIO_eof() calls feof().
44
45Setting the BIO_CLOSE flag calls fclose() on the stream when the BIO
46is freed.
47
48BIO_new_file() creates a new file BIO with mode B<mode> the meaning
49of B<mode> is the same as the stdio function fopen(). The BIO_CLOSE
50flag is set on the returned BIO.
51
52BIO_new_fp() creates a file BIO wrapping B<stream>. Flags can be:
53BIO_CLOSE, BIO_NOCLOSE (the close flag) BIO_FP_TEXT (sets the underlying
54stream to text mode, default is binary: this only has any effect under
55Win32).
56
57BIO_set_fp() sets the fp of a file BIO to B<fp>. B<flags> has the same
58meaning as in BIO_new_fp(), it is a macro.
59
60BIO_get_fp() retrieves the fp of a file BIO, it is a macro.
61
62BIO_seek() is a macro that sets the position pointer to B<offset> bytes
63from the start of file.
64
65BIO_tell() returns the value of the position pointer.
66
67BIO_read_filename(), BIO_write_filename(), BIO_append_filename() and
68BIO_rw_filename() set the file BIO B<b> to use file B<name> for
69reading, writing, append or read write respectively.
70
71=head1 NOTES
72
73When wrapping stdout, stdin or stderr the underlying stream should not
74normally be closed so the BIO_NOCLOSE flag should be set.
75
76Because the file BIO calls the underlying stdio functions any quirks
77in stdio behaviour will be mirrored by the corresponding BIO.
78
79On Windows BIO_new_files reserves for the filename argument to be
80UTF-8 encoded. In other words if you have to make it work in multi-
81lingual environment, encode filenames in UTF-8.
82
83=head1 RETURN VALUES
84
85BIO_s_file() returns the file BIO method.
86
87BIO_new_file() and BIO_new_fp() return a file BIO or NULL if an error
88occurred.
89
90BIO_set_fp() and BIO_get_fp() return 1 for success or <=0 for failure
91(although the current implementation never return 0).
92
93BIO_seek() returns 0 for success or negative values for failure.
94
95BIO_tell() returns the current file position or negative values for failure.
96
97BIO_read_filename(), BIO_write_filename(), BIO_append_filename() and
98BIO_rw_filename() return 1 for success or <=0 for failure.
99
100=head1 EXAMPLES
101
102File BIO "hello world":
103
104 BIO *bio_out;
105
106 bio_out = BIO_new_fp(stdout, BIO_NOCLOSE);
107 BIO_printf(bio_out, "Hello World\n");
108
109Alternative technique:
110
111 BIO *bio_out;
112
113 bio_out = BIO_new(BIO_s_file());
114 if (bio_out == NULL)
115     /* Error */
116 if (BIO_set_fp(bio_out, stdout, BIO_NOCLOSE) <= 0)
117     /* Error */
118 BIO_printf(bio_out, "Hello World\n");
119
120Write to a file:
121
122 BIO *out;
123
124 out = BIO_new_file("filename.txt", "w");
125 if (!out)
126     /* Error */
127 BIO_printf(out, "Hello World\n");
128 BIO_free(out);
129
130Alternative technique:
131
132 BIO *out;
133
134 out = BIO_new(BIO_s_file());
135 if (out == NULL)
136     /* Error */
137 if (BIO_write_filename(out, "filename.txt") <= 0)
138     /* Error */
139 BIO_printf(out, "Hello World\n");
140 BIO_free(out);
141
142=head1 BUGS
143
144BIO_reset() and BIO_seek() are implemented using fseek() on the underlying
145stream. The return value for fseek() is 0 for success or -1 if an error
146occurred this differs from other types of BIO which will typically return
1471 for success and a non positive value if an error occurred.
148
149=head1 SEE ALSO
150
151L<BIO_seek(3)>, L<BIO_tell(3)>,
152L<BIO_reset(3)>, L<BIO_flush(3)>,
153L<BIO_read_ex(3)>,
154L<BIO_write_ex(3)>, L<BIO_puts(3)>,
155L<BIO_gets(3)>, L<BIO_printf(3)>,
156L<BIO_set_close(3)>, L<BIO_get_close(3)>
157
158=head1 COPYRIGHT
159
160Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
161
162Licensed under the Apache License 2.0 (the "License").  You may not use
163this file except in compliance with the License.  You can obtain a copy
164in the file LICENSE in the source distribution or at
165L<https://www.openssl.org/source/license.html>.
166
167=cut
168