How to find out the size of a directory in adb shell?

I want to find out storage usage of an app. I can list file size in adb shell using ls command. But, I didn't find 'du' command in adb 开发者_如何学Goshell. Is there any command or tool that allows me to figure out the storage usage of a directory?

Thanks.

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There's no du in /system/bin. But you can push busybox to device, and use busybox's du.