--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/uprogs/forktest.c	Sun Oct 22 18:25:39 2017 +0900
@@ -0,0 +1,56 @@
+// Test that fork fails gracefully.
+// Tiny executable so that the limit can be filling the proc table.
+
+#include "types.h"
+#include "stat.h"
+#include "user.h"
+
+#define N  1000
+
+void
+printf(int fd, char *s, ...)
+{
+  write(fd, s, strlen(s));
+}
+
+void
+forktest(void)
+{
+  int n, pid;
+
+  printf(1, "fork test\n");
+
+  for(n=0; n<N; n++){
+    pid = fork();
+    if(pid < 0)
+      break;
+    if(pid == 0)
+      exit();
+  }
+  
+  if(n == N){
+    printf(1, "fork claimed to work N times!\n", N);
+    exit();
+  }
+  
+  for(; n > 0; n--){
+    if(wait() < 0){
+      printf(1, "wait stopped early\n");
+      exit();
+    }
+  }
+  
+  if(wait() != -1){
+    printf(1, "wait got too many\n");
+    exit();
+  }
+  
+  printf(1, "fork test OK\n");
+}
+
+int
+main(void)
+{
+  forktest();
+  exit();
+}