diff -u strace_4.0.orig.tar.gz#utar/strace-4.0/file.c strace/file.c
--- strace_4.0.orig.tar.gz#utar/strace-4.0/file.c	Fri Jul  9 02:32:54 1999
+++ strace/file.c	Sat Dec 11 23:53:14 1999
@@ -1397,6 +1397,10 @@
 				d->d_namlen, d->d_namlen, d->d_name);
 		}
 #endif /* SUNOS4 */
+		if (!d->d_reclen) {
+			tprintf("/* d_reclen == 0, problem here */");
+			break;
+		}
 		i += d->d_reclen;
 		dents++;
 	}
diff -u strace_4.0.orig.tar.gz#utar/strace-4.0/process.c strace/process.c
--- strace_4.0.orig.tar.gz#utar/strace-4.0/process.c	Fri Jun 11 15:18:40 1999
+++ strace/process.c	Sun Nov 21 22:17:43 1999
@@ -294,6 +294,21 @@
 }
 
 int
+change_syscall(tcp, new)
+struct tcb *tcp;
+int new;
+{
+#if defined(I386) && defined(LINUX)
+	/* Attempt to make vfork into fork, which we can follow. */
+	if (ptrace(PTRACE_POKEUSER, tcp->pid, 
+		   (void *)(ORIG_EAX * 4), new) < 0) 
+		return -1;
+	return 0;
+#endif
+	return -1;
+}
+
+int
 internal_fork(tcp)
 struct tcb *tcp;
 {
@@ -303,16 +318,10 @@
 
 #ifdef SYS_vfork
 	if (tcp->scno == SYS_vfork) {
-#if defined(I386) && defined(LINUX)
 		/* Attempt to make vfork into fork, which we can follow. */
 		if (!followvfork || 
-		    ptrace(PTRACE_POKEUSR, tcp->pid, 
-			   (void *)(ORIG_EAX * 4), SYS_fork) < 0) 
+		    change_syscall(tcp, SYS_fork) < 0)
 			dont_follow = 1;
-		
-#else
-		dont_follow = 1;
-#endif
 	}
 #endif
 #ifdef SYS_clone
diff -u strace_4.0.orig.tar.gz#utar/strace-4.0/strace.c strace/strace.c
--- strace_4.0.orig.tar.gz#utar/strace-4.0/strace.c	Mon Jun 28 15:17:16 1999
+++ strace/strace.c	Thu Dec  9 12:00:38 1999
@@ -59,7 +59,10 @@
 int acolumn = DEFAULT_ACOLUMN;
 int max_strlen = DEFAULT_STRLEN;
 char *outfname = NULL;
+char *filter = NULL;
+int filterf = -1;
 FILE *outf;
+int inf;
 struct tcb tcbtab[MAX_PROCS];
 int nprocs;
 char *progname;
@@ -170,7 +173,7 @@
 	set_sortby(DEFAULT_SORTBY);
 	set_personality(DEFAULT_PERSONALITY);
 	while ((c = getopt(argc, argv,
-		"+cdfFhiqrtTvVxa:e:o:O:p:s:S:u:")) != EOF) {
+		"+cdfFhiqrtTvVxa:e:o:O:p:s:S:u:y:")) != EOF) {
 		switch (c) {
 		case 'c':
 			cflag++;
@@ -223,6 +226,9 @@
 		case 'o':
 			outfname = strdup(optarg);
 			break;
+		case 'y':	/* Notice you can use something like ./strace -y 'cat >&2 | cat <&2' ls to filter interactively */
+			filter = strdup(optarg);
+			break;
 		case 'O':
 			set_overhead(atoi(optarg));
 			break;
@@ -233,8 +239,8 @@
 				break;
 			}
 			if (pid == getpid()) {
-				fprintf(stderr, "%s: I'm sorry, I can't let you do that, Dave.", progname);
-				break;
+				fprintf(stderr, "%s: I'm sorry, I can't let you do that, Dave.\n", progname);
+				exit(1);
 			}
 			if ((tcp = alloctcb(pid)) == NULL) {
 				fprintf(stderr, "%s: tcb table full, please recompile strace\n",
@@ -306,6 +312,28 @@
 		}
 	}
 
+	if (filter) {
+		int pin[2], pout[2];
+		pipe(pin);
+		pipe(pout);
+		if (!fork()) {	/* Child */
+			close(0);
+			dup(pin[0]);
+			close(1);
+			dup(pout[1]);
+			close(pin[0]);
+			close(pin[1]);
+			close(pout[0]);
+			close(pout[1]);
+			system( filter );
+			exit(0);
+		}
+		close(pin[0]);
+		close(pout[1]);
+		outf = fdopen(pin[1], "w");
+		filterf = pout[0];
+	}
+
 #ifndef SVR4
 	setreuid(geteuid(), getuid());
 #endif
diff -u strace_4.0.orig.tar.gz#utar/strace-4.0/syscall.c strace/syscall.c
--- strace_4.0.orig.tar.gz#utar/strace-4.0/syscall.c	Thu Jun 24 15:55:29 1999
+++ strace/syscall.c	Mon Nov 29 10:23:03 1999
@@ -1263,6 +1303,11 @@
 		sys_res = (*sysent[tcp->scno].sys_func)(tcp);
 	if (fflush(tcp->outf) == EOF)
 		return -1;
+
+	res = syscall_monitor(tcp);
+	if (res != 1)
+		return -1;
+
 	tcp->flags |= TCB_INSYSCALL;
 	/* Measure the entrance time as late as possible to avoid errors. */
 	if (dtime)
@@ -1454,4 +1499,32 @@
 	fprintf(outf, "%6.6s %4ld.%06ld %11.11s %9d %9.9s %s\n",
 		"100.00", (long) tv_cum.tv_sec, (long) tv_cum.tv_usec, "",
 		call_cum, error_str, "total");
+}
+
+static int
+syscall_monitor(tcp)
+struct tcb *tcp;
+{
+	char res = 0;
+	extern int filterf;
+
+	if (filterf == -1)
+		return 1;
+
+	tprintf( " ALLOW? (y/n/k)\n" );
+ retry:
+	if (fflush(tcp->outf) == EOF)
+		return -1;
+	if (read(filterf, &res, 1)!=1)
+		return -1;
+	switch(res) {
+	case 'n':
+		if (change_syscall(tcp, __NR_getpmsg) == 0)
+	case 'y':
+			return 1;
+	case 'k':
+		return -1;
+	default:
+		goto retry;
+	}
 }
diff -u strace_4.0.orig.tar.gz#utar/strace-4.0/util.c strace/util.c
--- strace_4.0.orig.tar.gz#utar/strace-4.0/util.c	Tue Jun 22 17:28:30 1999
+++ strace/util.c	Sat Dec 11 23:53:13 1999
@@ -318,6 +318,7 @@
 struct tcb *tcp;
 long addr;
 {
+	tprintf("(at: %x) ", tcp->u_arg[0]);
 	if (umovestr(tcp, addr, MAXPATHLEN, path) < 0)
 		tprintf("%#lx", addr);
 	else
@@ -331,6 +332,7 @@
 long addr;
 int n;
 {
+	tprintf("(at: %x) ", tcp->u_arg[0]);
 	if (umovestr(tcp, addr, n, path) < 0)
 		tprintf("%#lx", addr);
 	else {