FD(4) FD(4) NAME fd, stdin, stdout, stderr, tty - file descriptor files DESCRIPTION These files, conventionally called /dev/fd/0, /dev/fd/1, ... /dev/fd/127, refer to files accessible through file descrip- tors. If file descriptor n is open, these two system calls have the same effect: fd = open("/dev/fd/n", mode); fd = dup(n); Creat(2) is equivalent to open, and mode is ignored. As with dup, subsequent IO on fd fails unless the original file descriptor allows the read or write operation. Entry /dev/fd/3 is conventionally the `control terminal' of the process group to which the present process belongs; see stream(4). The entries /dev/stdin, /dev/stdout, /dev/stderr, and /dev/tty are conventionally linked to /dev/fd/0, /dev/fd/1, /dev/fd/2, and /dev/fd/3 respectively. SEE ALSO open(2), dup(2), stream(4) DIAGNOSTICS Open returns -1 if the related file descriptor is not open.