#include <u.h>#include <libc.h>#include <thread.h> typedef struct Exec Exec; struct Exec {	/* these two specify what program (and arguments) to run using procexec */	char *file;	char **argv; 	/* this will have either -1 or the actual pid of the executed program sent over */	Channel *pid;}; voidpexec(void *args){	Exec *e = args;	procexec(e->pid, e->file, e->argv);} voidthreadmain(int, char **){	Exec e;	int i, n, pid;	Channel *waitc;	Waitmsg *w;	char *argv[] = {"rc", "-c", "sleep 2", nil}; 	quotefmtinstall(); 	/* this HAS to be called before spawning other threads	 * otherwise those threads won't send their status	 */	waitc = threadwaitchan(); 	/* that's where we get the pid from */	e.pid = chancreate(sizeof(int), 0); 	for(n = i = 0; i < 3; n++, i++){		/* last process always fails to demonstrate the error status */		if(i == 2)			argv[2] = "this breaks";		e.file = "/bin/rc";		e.argv = argv;		proccreate(pexec, &e, 4096); 		/* receive the pid */		recv(e.pid, &pid);		if(pid < 0)			sysfatal("procexec failed"); 		fprint(2, "pid %d running\n", pid);	} 	/* won't get any new pids at this point */	chanfree(e.pid); 	/* wait until all processes are finished	 * we know how many there are so it's pretty easy	 */	while(n > 0){		/* w (Waitmsg) points to the result of a finished process */		w = recvp(waitc);		fprint(2, "pid %d: %q\n", w->pid, w->msg);		/* each one of them is allocated with malloc */		free(w);		n--;	} 	threadexitsall(nil);}