How to compile modules in Android with mm and MMM

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Methods of using mm and MMM:
1. Enter Android root directory: cd Your-android-source-path
2, will envsetup.sh source come in:. build/envsetup.sh (note: There are spaces behind)
3, after you can use mm and mmm. 
next to explain the difference between mm and MMM:
mm: Compile the current directory of the module, the current directory to have android.mk file. 
mmm path: Compiles the module under the specified path, specifying the path to the Android.mk file. 
Here is an example, let's say I want to compile the Libjpeg module under Android, the current directory is the source root directory, the method is as follows:
1,. build/envsetup.sh
2, MMM external/jpeg/or: 1,. build/envsetup.sh
2. CD External/jpeg
3, MM
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Excerpt from Baidu know

Note: not noticed before. There's a space behind.
Lunch platform required after envsetup.sh
Under the same terminal, do mm (different terminal tags are not)

How to compile modules in Android with mm and MMM