Updated Lua Examples (markdown)

Lua-Examples.md

@@ -2,7 +2,7 @@ By default Inbucket will load `inbucket.lua`, but you may use the `INBUCKET_LUA_
 
 ## Event trigger: after message stored
 
-Prints metadata of stored messages to STDOUT.
+Prints metadata of stored messages to STDOUT:
 
 ```lua
 function inbucket.after.message_stored(msg)
@@ -22,7 +22,7 @@ function inbucket.after.message_stored(msg)
 end
 ```
 
-Makes a JSON encoded POST to a web service.
+Makes a JSON encoded POST to a web service:
 
 ```lua
 local http = require("http")
@@ -41,4 +41,26 @@ function inbucket.after.message_stored(msg)
     body = request,
   }))
 end
+```
+
+Writes data to temporary file and runs external shell command:
+
+```lua
+function inbucket.after.message_stored(msg)
+  local content = string.format("%q,%q", msg.from, msg.subject)
+
+  -- Write POST data to temporary file.
+  local fnam = os.tmpname()
+  local f = assert(io.open(fnam, "w+"))
+  assert(f:write(content))
+  f:close()
+
+  local cmd = string.format("cat %q", fnam)
+  print(string.format("\n### running %s ###", cmd))
+  local status = os.execute(cmd)
+  if status ~= 0 then
+    error("command failed: " .. cmd)
+  end
+  print("\n")
+end
 ```