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); On these devices creat (see open(2)) is equivalent to open, and mode is ignored. As with dup, subsequent reads or writes on fd fail unless the original file descriptor allows the operations. FILES not open and in the appropriate mode (reading or writing).