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