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BIO_S_FILE(3)			    OpenSSL			 BIO_S_FILE(3)

       BIO_s_file, BIO_new_file, BIO_new_fp, BIO_set_fp, BIO_get_fp,
       BIO_read_filename, BIO_write_filename, BIO_append_filename,
       BIO_rw_filename - FILE bio

	#include <openssl/bio.h>

	const BIO_METHOD *BIO_s_file(void);
	BIO *BIO_new_file(const	char *filename,	const char *mode);
	BIO *BIO_new_fp(FILE *stream, int flags);

	BIO_set_fp(BIO *b, FILE	*fp, int flags);
	BIO_get_fp(BIO *b, FILE	**fpp);

	int BIO_read_filename(BIO *b, char *name)
	int BIO_write_filename(BIO *b, char *name)
	int BIO_append_filename(BIO *b,	char *name)
	int BIO_rw_filename(BIO	*b, char *name)

       BIO_s_file() returns the	BIO file method. As its	name implies it	is a
       wrapper round the stdio FILE structure and it is	a source/sink BIO.

       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

       BIO_flush() on a	file BIO calls the fflush() function on	the wrapped

       BIO_reset() attempts to change the file pointer to the start of file
       using fseek(stream, 0, 0).

       BIO_seek() sets the file	pointer	to position ofs	from start of file
       using fseek(stream, ofs,	0).

       BIO_eof() calls feof().

       Setting the BIO_CLOSE flag calls	fclose() on the	stream when the	BIO is

       BIO_new_file() creates a	new file BIO with mode mode the	meaning	of
       mode is the same	as the stdio function fopen(). The BIO_CLOSE flag is
       set on the returned BIO.

       BIO_new_fp() creates a file BIO wrapping	stream.	Flags can be:
       BIO_CLOSE, BIO_NOCLOSE (the close flag) BIO_FP_TEXT (sets the
       underlying stream to text mode, default is binary: this only has	any
       effect under Win32).

       BIO_set_fp() sets the fp	of a file BIO to fp. flags has the same
       meaning as in BIO_new_fp(), it is a macro.

       BIO_get_fp() retrieves the fp of	a file BIO, it is a macro.

       BIO_seek() is a macro that sets the position pointer to offset bytes
       from the	start of file.

       BIO_tell() returns the value of the position pointer.

       BIO_read_filename(), BIO_write_filename(), BIO_append_filename()	and
       BIO_rw_filename() set the file BIO b to use file	name for reading,
       writing,	append or read write respectively.

       When wrapping stdout, stdin or stderr the underlying stream should not
       normally	be closed so the BIO_NOCLOSE flag should be set.

       Because the file	BIO calls the underlying stdio functions any quirks in
       stdio behaviour will be mirrored	by the corresponding BIO.

       On Windows BIO_new_files	reserves for the filename argument to be UTF-8
       encoded.	In other words if you have to make it work in multi- lingual
       environment, encode filenames in	UTF-8.

       BIO_s_file() returns the	file BIO method.

       BIO_new_file() and BIO_new_fp() return a	file BIO or NULL if an error

       BIO_set_fp() and	BIO_get_fp() return 1 for success or 0 for failure
       (although the current implementation never return 0).

       BIO_seek() returns the same value as the	underlying fseek() function: 0
       for success or -1 for failure.

       BIO_tell() returns the current file position.

       BIO_read_filename(), BIO_write_filename(), BIO_append_filename()	and
       BIO_rw_filename() return	1 for success or 0 for failure.

       File BIO	"hello world":

	BIO *bio_out;

	bio_out	= BIO_new_fp(stdout, BIO_NOCLOSE);
	BIO_printf(bio_out, "Hello World\n");

       Alternative technique:

	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\n");

       Write to	a file:

	BIO *out;

	out = BIO_new_file("filename.txt", "w");
	if (!out)
	    /* Error */
	BIO_printf(out,	"Hello World\n");

       Alternative technique:

	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\n");

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

       BIO_seek(3), BIO_tell(3), BIO_reset(3), BIO_flush(3), BIO_read_ex(3),
       BIO_write_ex(3),	BIO_puts(3), BIO_gets(3), BIO_printf(3),
       BIO_set_close(3), BIO_get_close(3)

       Copyright 2000-2020 The OpenSSL Project Authors.	All Rights Reserved.

       Licensed	under the OpenSSL license (the "License").  You	may not	use
       this file except	in compliance with the License.	 You can obtain	a copy
       in the file LICENSE in the source distribution or at

1.1.1k				  2021-03-25			 BIO_S_FILE(3)


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