diff --git a/rt3.lua b/rt3.lua
new file mode 100755
index 0000000..d517ea3
--- /dev/null
+++ b/rt3.lua
@@ -0,0 +1,10 @@
+#!/usr/bin/env lua
+require "ex"
+
+print"os.chdir"
+assert(os.chdir(".."))
+print(os.currentdir())
+
+print"os.mkdir"
+assert(os.mkdir("Foo.test"))
+assert(os.chdir("Foo.test"))
diff --git a/rt4.lua b/rt4.lua
new file mode 100755
index 0000000..606bf4f
--- /dev/null
+++ b/rt4.lua
@@ -0,0 +1,10 @@
+#!/usr/bin/env lua
+require "ex"
+
+local f = assert(io.open("hullo.test", "w+"))
+f:lock("w")
+f:write("Hello\n")
+f:unlock()
+f:seek("set")
+print(f:read())
+f:close()
diff --git a/rt5.lua b/rt5.lua
new file mode 100755
index 0000000..15759fa
--- /dev/null
+++ b/rt5.lua
@@ -0,0 +1,8 @@
+#!/usr/bin/env lua
+require "ex"
+
+local proc
+proc = assert(os.spawn(arg[1]))
+print(proc)
+os.sleep(3)
+proc:wait()