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BIO_S_FILE(3)                       OpenSSL                      BIO_S_FILE(3)
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 filenames in UTF-8.
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.
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);
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 2000-2020 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
       <https://www.openssl.org/source/license.html>;.
1.1.1k                            2021-03-25                     BIO_S_FILE(3)