#include <stdio.h> FILE *popen(char *cmd, char *type){	int p[2], r, null, pid;	FILE *s; 	pipe(p);	r = type[0] == 'r' || type[1] == 'r';	if((pid = rfork(RFPROC|RFFDG|RFNOTEG|RFCENVG|RFNOWAIT)) == 0){		null = open("/dev/null", r ? OWRITE : OREAD);		dup(null, !r);		dup(p[r], r);		close(p[r]);		close(null);		execl("/bin/rc", "rc", "-c", cmd, nil);		sysfatal("popen: execl: %r");	}else if(pid < 0){		close(p[0]);		close(p[1]);		return nil;	}	s = fdopen(p[!r], r ? "r" : "w");	close(p[r]);	return s;}