How to observe the content of static lib in mac OS?

I create a static library project in my xCode and build a .a named mylib.a. There some code (.m files) and another static lib file named common.a to inform the static library nylib.a. But I doubt that if the contend of common.a are pack in the mylib.a really. So how can I observe the content of the mylib.a in mac OS? I knew there are some command such as ar, nm to complete this task in Linux. but It does't run in mac OS.