the transport for the communication pipe corresponding to the integer file descriptor fd:
0: readable streaming transport of the standard input (stdin), or throws $(D_PSYMBOL Exception) if the subprocess was not created with stdin = PIPE 1: writable streaming transport of the standard output (stdout), or throws $(D_PSYMBOL Exception) if the subprocess was not created with stdout = PIPE 2: writable streaming transport of the standard error (stderr), or throws $(D_PSYMBOL Exception) if the subprocess was not created with stderr = PIPE other fd: throws $(D_PSYMBOL Exception)