diff -NU3 src.orig/svscan.c src/svscan.c
--- src.orig/svscan.c	Thu Jul 12 18:49:49 2001
+++ src/svscan.c	Sun Sep  9 00:31:25 2001
@@ -11,6 +11,8 @@
 #include "str.h"
 #include "byte.h"
 #include "pathexec.h"
+#include "open.h"
+#include "lock.h"
 
 #define SERVICES 1000
 
@@ -192,10 +194,17 @@
 
 int main(int argc,char **argv)
 {
+  int fd;
   if (argv[0] && argv[1])
     if (chdir(argv[1]) == -1)
       strerr_die4sys(111,FATAL,"unable to chdir to ",argv[1],": ");
 
+  fd = open_append(".svscan-lock");
+  if (fd == -1)
+    strerr_die2sys(111,FATAL,"unable to open lock file: ");
+  if (lock_exnb(fd) == -1)
+    strerr_die2sys(111,FATAL,"unable to get lock: ");
+  coe(fd);
   for (;;) {
     doit();
     sleep(5);