NAME

       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

SYNOPSIS

        #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)

DESCRIPTION

       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 BIOs.

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

       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 freed.

       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.

NOTES

       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 file names in
       UTF-8.

EXAMPLES

       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");
        BIO_free(out);

       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_free(out);

RETURN VALUES

       BIO_s_file() returns the file BIO method.

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

       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.

BUGS

       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 occurred.

SEE ALSO

       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

       Copyright 2000-2018 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 <https://www.openssl.org/source/license.html>.