- NAME
- SYNOPSIS
- DESCRIPTION
- NOTES
- RETURN VALUES
- EXAMPLE
- SEE ALSO

# NAME

BIO_s_fd, BIO_set_fd, BIO_get_fd, BIO_new_fd - file descriptor BIO

# SYNOPSIS

     #include <openssl/bio.h>

     BIO_METHOD *   BIO_s_fd(void);

     #define BIO_set_fd(b,fd,c)     BIO_int_ctrl(b,BIO_C_SET_FD,c,fd)
     #define BIO_get_fd(b,c)        BIO_ctrl(b,BIO_C_GET_FD,0,(char *)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()` and `BIO_write()` read or write the underlying descriptor. `BIO_puts()` is supported but `BIO_gets()` is not.

If the close flag is set then 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 using lseek(fd, 0, 0).

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

`BIO_tell()` returns the current file position 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. If c is not NULL it should be of type (int *).

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

# NOTES

The behaviour of `BIO_read()` and `BIO_write()` 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 and BIO_should_retry manual pages.

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

# RETURN VALUES

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

`BIO_reset()` returns zero for success and -1 if an error occurred. `BIO_seek()` and `BIO_tell()` return the current file position or -1 is an error occurred. These values reflect the underlying `lseek()` behaviour.

`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.

# EXAMPLE

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, BIO_tell, BIO_reset, BIO_read, BIO_write, BIO_puts, BIO_gets, BIO_printf, BIO_set_close, BIO_get_close