$ adb --help
-s SERIAL use device with given serial (overrides $ANDROID_SERIAL)
$ adb devices List of devices attached emulator-5554 device 7f1c864e device
$ adb shell -s 7f1c864e error: more than one device and emulator
使用-s命令前的选项指定设备，例如：
-s
adb -s 7f1c864e shell
另请参阅http://developer.android.com/tools/help/adb.html#directingcommands
