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Title "BIO_s_file 3"
way too many mistakes in technical documents.
.nh
Calls to BIO_read_ex() and BIO_write_ex() read and write data to the underlying stream. BIO_gets() and BIO_puts() are supported on file BIOs.
\fBBIO_flush() on a file \s-1BIO\s0 calls the fflush() function on the wrapped stream.
\fBBIO_reset() attempts to change the file pointer to the start of file using fseek(stream, 0, 0).
\fBBIO_seek() sets the file pointer to position ofs from start of file using fseek(stream, ofs, 0).
\fBBIO_eof() calls feof().
Setting the \s-1BIO_CLOSE\s0 flag calls fclose() on the stream when the \s-1BIO\s0 is freed.
\fBBIO_new_file() creates a new file \s-1BIO\s0 with mode mode the meaning of mode is the same as the stdio function fopen(). The \s-1BIO_CLOSE\s0 flag is set on the returned \s-1BIO.\s0
\fBBIO_new_fp() creates a file \s-1BIO\s0 wrapping stream. Flags can be: \s-1BIO_CLOSE, BIO_NOCLOSE\s0 (the close flag) \s-1BIO_FP_TEXT\s0 (sets the underlying stream to text mode, default is binary: this only has any effect under Win32).
\fBBIO_set_fp() sets the fp of a file \s-1BIO\s0 to fp. flags has the same meaning as in BIO_new_fp(), it is a macro.
\fBBIO_get_fp() retrieves the fp of a file \s-1BIO,\s0 it is a macro.
\fBBIO_seek() is a macro that sets the position pointer to offset bytes from the start of file.
\fBBIO_tell() returns the value of the position pointer.
\fBBIO_read_filename(), BIO_write_filename(), BIO_append_filename() and \fBBIO_rw_filename() set the file \s-1BIO\s0 b to use file name for reading, writing, append or read write respectively.
Because the file \s-1BIO\s0 calls the underlying stdio functions any quirks in stdio behaviour will be mirrored by the corresponding \s-1BIO.\s0
On Windows BIO_new_files reserves for the filename argument to be \s-1UTF-8\s0 encoded. In other words if you have to make it work in multi- lingual environment, encode filenames in \s-1UTF-8.\s0
\fBBIO_new_file() and BIO_new_fp() return a file \s-1BIO\s0 or \s-1NULL\s0 if an error occurred.
\fBBIO_set_fp() and BIO_get_fp() return 1 for success or 0 for failure (although the current implementation never return 0).
\fBBIO_seek() returns the same value as the underlying fseek() function: 0 for success or -1 for failure.
\fBBIO_tell() returns the current file position.
\fBBIO_read_filename(), BIO_write_filename(), BIO_append_filename() and \fBBIO_rw_filename() return 1 for success or 0 for failure.
.Vb 1 BIO *bio_out; \& bio_out = BIO_new_fp(stdout, BIO_NOCLOSE); BIO_printf(bio_out, "Hello World\en"); .Ve
Alternative technique:
.Vb 1 BIO *bio_out; \& bio_out = BIO_new(BIO_s_file()); if (bio_out == NULL) /* Error */ if (!BIO_set_fp(bio_out, stdout, BIO_NOCLOSE)) /* Error */ BIO_printf(bio_out, "Hello World\en"); .Ve
Write to a file:
.Vb 1 BIO *out; \& out = BIO_new_file("filename.txt", "w"); if (!out) /* Error */ BIO_printf(out, "Hello World\en"); BIO_free(out); .Ve
Alternative technique:
.Vb 1 BIO *out; \& out = BIO_new(BIO_s_file()); if (out == NULL) /* Error */ if (!BIO_write_filename(out, "filename.txt")) /* Error */ BIO_printf(out, "Hello World\en"); BIO_free(out); .Ve
Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.
Indexes created Wed Apr 22 00:22:44 UTC 2026