use EARGF where appropriate.  hopefully a conservative list.  i tried not to change default behaviors.
just address potential indirection of zero and bad system call arguments.

Notes:
Sat Oct 21 10:47:05 EDT 2006 rsc
    Thanks.  Please build these before submitting though -- you
    had a typo in  yacc.c.


Reference: /n/sources/patch/applied/eargf1
Date: Tue Sep 26 03:09:34 CES 2006
Signed-off-by: quanstro@quanstro.net
Reviewed-by: rsc

--- /sys/src/cmd/srvfs.c	Tue Sep 26 03:02:15 2006
+++ /sys/src/cmd/srvfs.c	Tue Sep 26 03:02:10 2006
@@ -26,14 +26,14 @@
 		*argp++ = "-d";
 		break;
 	case 'e':
-		ename = ARGF();
+		ename = EARGF(usage());
 		break;
 	case 'p':
-		perm = strtol(ARGF(), 0, 8);
+		perm = strtol(EARGF(usage()), 0, 8);
 		break;
 	case 'P':
 		*argp++ = "-P";
-		*argp++ = ARGF();
+		*argp++ = EARGF(usage());
 		break;
 	case 'R':
 		*argp++ = "-R";
--- /sys/src/cmd/archfs.c	Tue Sep 26 03:02:37 2006
+++ /sys/src/cmd/archfs.c	Tue Sep 26 03:02:32 2006
@@ -213,7 +213,7 @@
 		flag |= MCACHE;
 		break;
 	case 'm':
-		mtpt = ARGF();
+		mtpt = EARGF(usage());
 		break;
 	default:
 		usage();
--- /sys/src/cmd/seq.c	Tue Sep 26 03:03:03 2006
+++ /sys/src/cmd/seq.c	Tue Sep 26 03:02:58 2006
@@ -58,7 +58,7 @@
 		constant++;
 		break;
 	case 'f':
-		format = ARGF();
+		format = EARGF(usage());
 		if(format[strlen(format)-1] != '\n'){
 			sprint(ffmt, "%s\n", format);
 			format = ffmt;
--- /sys/src/cmd/tlssrv.c	Tue Sep 26 03:03:33 2006
+++ /sys/src/cmd/tlssrv.c	Tue Sep 26 03:03:28 2006
@@ -103,6 +103,14 @@
 }
 
 void
+usage(void)
+{
+	fprint(2, "usage: tlssrv -c cert [-D] [-l logfile] [-r remotesys] [cmd args...]\n");
+	fprint(2, "  after  auth/secretpem key.pem > /mnt/factotum/ctl\n");
+	exits("usage");
+}
+
+void
 main(int argc, char *argv[])
 {
 	TLSconn *conn;
@@ -119,18 +127,16 @@
 		debug++;
 		break;
 	case 'c':
-		cert = ARGF();
+		cert = EARGF(usage());
 		break;
 	case 'l':
-		logfile = ARGF();
+		logfile = EARGF(usage());
 		break;
 	case 'r':
-		remotesys = ARGF();
+		remotesys = EARGF(usage());
 		break;
 	default:
-		fprint(2, "usage: tlssrv -c cert [-D] [-l logfile] [-r remotesys] [cmd args...]\n");
-		fprint(2, "  after  auth/secretpem key.pem > /mnt/factotum/ctl\n");
-		exits("usage");
+		usage();
 	}ARGEND
 
 	if(cert == nil)
--- /sys/src/cmd/calendar.c	Tue Sep 26 03:04:08 2006
+++ /sys/src/cmd/calendar.c	Tue Sep 26 03:04:03 2006
@@ -23,6 +23,13 @@
 void *emalloc(unsigned int);
 
 void
+usage(void)
+{
+	fprint(2, "usage: calendar [-dy] [-p days] [files ...]\n");
+	exits("usage");
+}
+
+void
 main(int argc, char *argv[])
 {
 	int i, fd, ahead;
@@ -41,11 +48,10 @@
 		debug = 1;
 		break;
 	case 'p':
-		ahead = atoi(ARGF());
+		ahead = atoi(EARGF(usage()));
 		break;
 	default:
-		fprint(2, "usage: calendar [-dy] [-p days] [files ...]\n");
-		exits("usage");
+		usage();
 	}ARGEND;
 
 	/* make a list of dates */
--- /sys/src/cmd/hget.c	Tue Sep 26 03:05:01 2006
+++ /sys/src/cmd/hget.c	Tue Sep 26 03:04:45 2006
@@ -120,7 +120,7 @@
 
 	ARGBEGIN {
 	case 'o':
-		ofile = ARGF();
+		ofile = EARGF(usage());
 		break;
 	case 'd':
 		debug = 1;
@@ -132,14 +132,10 @@
 		verbose = 1;
 		break;
 	case 'x':
-		net = ARGF();
-		if(net == nil)
-			usage();
+		net = EARGF(usage());
 		break;
 	case 'p':
-		t = ARGF();
-		if(t == nil)
-			usage();
+		t = EARGF(usage());
 		if(p != postbody)
 			p = seprint(p, e, "&%s", t);
 		else
--- /sys/src/cmd/yacc.c	Tue Sep 26 03:06:20 2006
+++ /sys/src/cmd/yacc.c	Tue Sep 26 03:05:48 2006
@@ -1164,6 +1164,13 @@
 }
 
 void
+usage(void)
+{
+	fprint(2, "usage: yacc [-Dn] [-vdS] [-o outputfile] [-s stem] grammar\n");
+	exits("usage");
+}
+
+void
 setup(int argc, char *argv[])
 {
 	long c, t;
@@ -1185,14 +1192,14 @@
 		vflag++;
 		break;
 	case 'D':
-		yydebug = ARGF();
+		yydebug = EARGF(usage());
 		break;
 	case 'd':
 		dflag++;
 		break;
 	case 'o':
 		ytab++;
-		ytabc = ARGF();
+		ytabc = ARGF(usage());
 		break;
 	case 's':
 		stem++;