- NAME
- SYNOPSIS
- DESCRIPTION
- NOTES
- RETURN VALUES
- EXAMPLES
- BUGS
- SEE ALSO
- COPYRIGHT

# 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.

# 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 2000-2019 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.