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

# NAME

BIO_s_fd, BIO_set_fd, BIO_get_fd, BIO_new_fd - file descriptor BIO

# SYNOPSIS

     #include <openssl/bio.h>

     const BIO_METHOD *BIO_s_fd(void);

     int BIO_set_fd(BIO *b, int fd, int c);
     int BIO_get_fd(BIO *b, int *c);

     BIO *BIO_new_fd(int fd, int close_flag);

# DESCRIPTION

`BIO_s_fd()` returns the file descriptor BIO method. This is a wrapper round the platforms file descriptor routines such as `read()` and `write()`.

`BIO_read_ex()` and `BIO_write_ex()` read or write the underlying descriptor. `BIO_puts()` is supported but `BIO_gets()` is not.

If the close flag is set then `close()` is called on the underlying file descriptor when the BIO is freed.

`BIO_reset()` attempts to change the file pointer to the start of file such as by using lseek(fd, 0, 0).

`BIO_seek()` sets the file pointer to position ofs from start of file such as by using lseek(fd, ofs, 0).

`BIO_tell()` returns the current file position such as by calling lseek(fd, 0, 1).

`BIO_set_fd()` sets the file descriptor of BIO b to fd and the close flag to c.

`BIO_get_fd()` places the file descriptor in c if it is not NULL, it also returns the file descriptor.

`BIO_new_fd()` returns a file descriptor BIO using fd and close_flag.

# NOTES

The behaviour of `BIO_read_ex()` and `BIO_write_ex()` depends on the behavior of the platforms `read()` and `write()` calls on the descriptor. If the underlying file descriptor is in a non blocking mode then the BIO will behave in the manner described in the BIO_read_ex(3) and BIO_should_retry(3) manual pages.

File descriptor BIOs should not be used for socket I/O. Use socket BIOs instead.

`BIO_set_fd()` and `BIO_get_fd()` are implemented as macros.

# RETURN VALUES

`BIO_s_fd()` returns the file descriptor BIO method.

`BIO_set_fd()` always returns 1.

`BIO_get_fd()` returns the file descriptor or -1 if the BIO has not been initialized.

`BIO_new_fd()` returns the newly allocated BIO or NULL is an error occurred.

# EXAMPLES

This is a file descriptor BIO version of "Hello World":

     BIO *out;

     out = BIO_new_fd(fileno(stdout), BIO_NOCLOSE);
     BIO_printf(out, "Hello World\n");
     BIO_free(out);

# SEE ALSO

BIO_seek(3), BIO_tell(3), BIO_reset(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.