Add file output

digwatch.yaml

@@ -8,8 +8,8 @@ syslog_output:
   enabled: false
 
 file_output:
-  enabled: false
-  filename: "bla.bla"
+  enabled: true
+  filename: ./events.txt
 
 stdout_output:
   enabled: true

userspace/digwatch/digwatch.cpp

@@ -184,8 +184,7 @@ void add_output(lua_State *ls, output_config oc)
 	if(lua_pcall(ls, nargs, 0, 0) != 0)
 	{
 		const char* lerr = lua_tostring(ls, -1);
-		string err = "Error invoking add_output: " + string(lerr);
-		throw sinsp_exception(err);
+		throw sinsp_exception(string(lerr));
 	}
 
 }

userspace/digwatch/lua/output.lua

@@ -9,6 +9,29 @@ function mod.stdout(evt, level, format)
    print (msg)
 end
 
+function mod.file_validate(options)
+   if (not type(options.filename) == 'string') then
+      error("File output needs to be configured with a valid filename")
+   end
+
+   file, err = io.open(options.filename, "a+")
+   if file == nil then
+      error("Error with file output: "..err)
+   end
+   file:close()
+
+end
+
+function mod.file(evt, level, format, options)
+   format = "%evt.time: "..levels[level+1].." "..format
+   formatter = digwatch.formatter(format)
+   msg = digwatch.format_event(evt, formatter)
+
+   file = io.open(options.filename, "a+")
+   file:write(msg, "\n")
+   file:close()
+end
+
 function mod.syslog(evt, level, format)
 
    formatter = digwatch.formatter(format)

userspace/digwatch/lua/rule_loader.lua

@@ -168,6 +168,12 @@ function add_output(output_name, config)
       error("rule_loader.add_output(): invalid output_name: "..output_name)
    end
 
+   -- outputs can optionally define a validation function so that we don't
+   -- find out at runtime (when an event finally matches a rule!) that the config is invalid
+   if (type(output_functions[output_name.."_validate"]) == 'function') then
+     output_functions[output_name.."_validate"](config)
+   end
+
    table.insert(outputs, {output = output_functions[output_name], config=config})
 end