/* * lock - keep a lock alive while a command runs */ #include <u.h>#include <libc.h>#include <ctype.h> static int debug;static int lockwait; void	error(char*);void	notifyf(void*, char*); static voidusage(void){	fprint(2, "usage: %s [-dw] lock [command [file]...]\n", argv0);	exits("usage");} static Waitmsg *waitfor(int pid){	char err[ERRMAX];	Waitmsg *w; 	for (;;) {		w = wait();		if (w == nil){			errstr(err, sizeof err);			if(strcmp(err, "interrupted") == 0)				continue;			return nil;		}		if (w->pid == pid)			return w;	}} static intopenlock(char *lock){	int lckfd;	Dir *dir; 	if (lockwait)		while ((lckfd = open(lock, ORDWR)) < 0)			sleep(1000);	else		lckfd = open(lock, ORDWR);	if (lckfd < 0)		sysfatal("can't open %s read/write: %r", lock);	dir = dirfstat(lckfd);	if (dir == nil)		sysfatal("can't fstat %s: %r", lock);	if (!(dir->mode & DMEXCL)) {		dir->mode |= DMEXCL;		dir->qid.type |= QTEXCL;		if (dirfwstat(lckfd, dir) < 0)			sysfatal("can't make %s exclusive access: %r", lock);	}	free(dir);	return lckfd;} voidmain(int argc, char *argv[]){	int fd, lckfd, lckpid, cmdpid;	char *cmd, *p, *lock;	char **args;	char *argarr[2];	Waitmsg *w; 	ARGBEGIN {	case 'd':		++debug;		break;	case 'w':		++lockwait;		break;	default:		usage();		break;	} ARGEND 	if (argc < 1)		usage();	if (argc == 1) {		args = argarr;		args[0] = cmd = "rc";		args[1] = nil;	} else {		cmd = argv[1];		args = &argv[1];	} 	/* set up lock and process to keep it alive */	lock = argv[0];	lckfd = openlock(lock);	lckpid = fork();	switch(lckpid){	case -1:		error("fork");	case 0:		/* keep lock alive until killed */		for (;;) {			sleep(60*1000);			seek(lckfd, 0, 0);			fprint(lckfd, "\n");		}	} 	/* spawn argument command */	cmdpid = rfork(RFFDG|RFREND|RFPROC|RFENVG);	switch(cmdpid){	case -1:		error("fork");	case 0:		fd = create("/env/prompt", OWRITE, 0666);		if (fd >= 0) {			fprint(fd, "%s%% ", lock);			close(fd);		}		exec(cmd, args);		if(cmd[0] != '/' && strncmp(cmd, "./", 2) != 0 &&		   strncmp(cmd, "../", 3) != 0)			exec(smprint("/bin/%s", cmd), args);		error(cmd);	} 	notify(notifyf); 	w = waitfor(cmdpid);	if (w == nil)		error("wait"); 	postnote(PNPROC, lckpid, "die");	waitfor(lckpid);	if(w->msg[0]){		p = utfrune(w->msg, ':');		if(p && p[1])			p++;		else			p = w->msg;		while (isspace(*p))			p++;		fprint(2, "%s: %s  # status=%s\n", argv0, cmd, p);	}	exits(w->msg);} voiderror(char *s){	fprint(2, "%s: %s: %r\n", argv0, s);	exits(s);} voidnotifyf(void *a, char *s){	USED(a);	if(strcmp(s, "interrupt") == 0)		noted(NCONT);	noted(NDFLT);}