Method: IO#fileno

Defined in:

io.c

#fileno ⇒ Integer Also known as: to_i

Returns the integer file descriptor for the stream:

$stdin.fileno             # => 0
$stdout.fileno            # => 1
$stderr.fileno            # => 2
File.open('t.txt').fileno # => 10
f.close

Returns:

• (Integer)

# File 'io.c', line 2886

static VALUE
rb_io_fileno(VALUE io)
{
    rb_io_t *fptr = RFILE(io)->fptr;
    int fd;

    rb_io_check_closed(fptr);
    fd = fptr->fd;
    return INT2FIX(fd);
}