add env command

main.go

@@ -8,15 +8,18 @@ import (
 func commandsUsage() string {
 	return fmt.Sprintf(
 		`commands:
+  env         %v
   path        %v
   time        %v
   week        %v
-`, commandPathDescription, commandTimeDescription, commandWeekDescription)
+`, commandEnvDescription, commandPathDescription, commandTimeDescription, commandWeekDescription)
 }
 
 func main() {
 	if len(os.Args) >= 2 {
 		switch os.Args[1] {
+		case "env":
+			commandEnv(os.Args[1:])
 		case "path":
 			commandPath(os.Args[1:])
 		case "time":