1BIO_S_FILE(3)                       OpenSSL                      BIO_S_FILE(3)
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NAME

6       BIO_s_file, BIO_new_file, BIO_new_fp, BIO_set_fp, BIO_get_fp,
7       BIO_read_filename, BIO_write_filename, BIO_append_filename,
8       BIO_rw_filename - FILE bio
9

SYNOPSIS

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

DESCRIPTION

26       BIO_s_file() returns the BIO file method. As its name implies it is a
27       wrapper round the stdio FILE structure and it is a source/sink BIO.
28
29       Calls to BIO_read_ex() and BIO_write_ex() read and write data to the
30       underlying stream. BIO_gets() and BIO_puts() are supported on file
31       BIOs.
32
33       BIO_flush() on a file BIO calls the fflush() function on the wrapped
34       stream.
35
36       BIO_reset() attempts to change the file pointer to the start of file
37       using fseek(stream, 0, 0).
38
39       BIO_seek() sets the file pointer to position ofs from start of file
40       using fseek(stream, ofs, 0).
41
42       BIO_eof() calls feof().
43
44       Setting the BIO_CLOSE flag calls fclose() on the stream when the BIO is
45       freed.
46
47       BIO_new_file() creates a new file BIO with mode mode the meaning of
48       mode is the same as the stdio function fopen(). The BIO_CLOSE flag is
49       set on the returned BIO.
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51       BIO_new_fp() creates a file BIO wrapping stream. Flags can be:
52       BIO_CLOSE, BIO_NOCLOSE (the close flag) BIO_FP_TEXT (sets the
53       underlying stream to text mode, default is binary: this only has any
54       effect under Win32).
55
56       BIO_set_fp() sets the fp of a file BIO to fp. flags has the same
57       meaning as in BIO_new_fp(), it is a macro.
58
59       BIO_get_fp() retrieves the fp of a file BIO, it is a macro.
60
61       BIO_seek() is a macro that sets the position pointer to offset bytes
62       from the start of file.
63
64       BIO_tell() returns the value of the position pointer.
65
66       BIO_read_filename(), BIO_write_filename(), BIO_append_filename() and
67       BIO_rw_filename() set the file BIO b to use file name for reading,
68       writing, append or read write respectively.
69

NOTES

71       When wrapping stdout, stdin or stderr the underlying stream should not
72       normally be closed so the BIO_NOCLOSE flag should be set.
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74       Because the file BIO calls the underlying stdio functions any quirks in
75       stdio behaviour will be mirrored by the corresponding BIO.
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77       On Windows BIO_new_files reserves for the filename argument to be UTF-8
78       encoded. In other words if you have to make it work in multi- lingual
79       environment, encode filenames in UTF-8.
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RETURN VALUES

82       BIO_s_file() returns the file BIO method.
83
84       BIO_new_file() and BIO_new_fp() return a file BIO or NULL if an error
85       occurred.
86
87       BIO_set_fp() and BIO_get_fp() return 1 for success or 0 for failure
88       (although the current implementation never return 0).
89
90       BIO_seek() returns the same value as the underlying fseek() function: 0
91       for success or -1 for failure.
92
93       BIO_tell() returns the current file position.
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95       BIO_read_filename(), BIO_write_filename(), BIO_append_filename() and
96       BIO_rw_filename() return 1 for success or 0 for failure.
97

EXAMPLES

99       File BIO "hello world":
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101        BIO *bio_out;
102
103        bio_out = BIO_new_fp(stdout, BIO_NOCLOSE);
104        BIO_printf(bio_out, "Hello World\n");
105
106       Alternative technique:
107
108        BIO *bio_out;
109
110        bio_out = BIO_new(BIO_s_file());
111        if (bio_out == NULL)
112            /* Error */
113        if (!BIO_set_fp(bio_out, stdout, BIO_NOCLOSE))
114            /* Error */
115        BIO_printf(bio_out, "Hello World\n");
116
117       Write to a file:
118
119        BIO *out;
120
121        out = BIO_new_file("filename.txt", "w");
122        if (!out)
123            /* Error */
124        BIO_printf(out, "Hello World\n");
125        BIO_free(out);
126
127       Alternative technique:
128
129        BIO *out;
130
131        out = BIO_new(BIO_s_file());
132        if (out == NULL)
133            /* Error */
134        if (!BIO_write_filename(out, "filename.txt"))
135            /* Error */
136        BIO_printf(out, "Hello World\n");
137        BIO_free(out);
138

BUGS

140       BIO_reset() and BIO_seek() are implemented using fseek() on the
141       underlying stream. The return value for fseek() is 0 for success or -1
142       if an error occurred this differs from other types of BIO which will
143       typically return 1 for success and a non positive value if an error
144       occurred.
145

SEE ALSO

147       BIO_seek(3), BIO_tell(3), BIO_reset(3), BIO_flush(3), BIO_read_ex(3),
148       BIO_write_ex(3), BIO_puts(3), BIO_gets(3), BIO_printf(3),
149       BIO_set_close(3), BIO_get_close(3)
150

COPYRIGHT

152       Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
153
154       Licensed under the OpenSSL license (the "License").  You may not use
155       this file except in compliance with the License.  You can obtain a copy
156       in the file LICENSE in the source distribution or at
157       <https://www.openssl.org/source/license.html>.
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1611.1.1i                            2021-01-26                     BIO_S_FILE(3)