Android linux环境变量

Question

I was poking around the /proc directory on my android device through adb shell, and looked at the contents of the environ file for one of the processes. The list of environment variables is as follows:

• PATH
• LD_LIBRARY_PATH
• ANDROID_BOOTLOGO
• ANDROID_ROOT
• ANDROID_ASSETS
• ANDROID_DATA
• ANDROID_STORAGE
• ASEC_MOUNTPOINT
• LOOP_MOUNTPOINT
• BOOTCLASSPATH
• EXTERNAL_STORAGE
• EMULATED_STORAGE_SOURCE
• EMULATED_STORAGE_TARGET
• ANDROID_PROPERTY_WORKSPACE
• ANDROID_SOCKET_zygote

This is list is different from the environment variables seen in Linux. When I see the environ file of some process on my ubuntu-12.04, I see a list much longer and very different (only PATH is same).

I have the following questions:

• where does Android define the environment variables ?

  Since the environ file in Android is different from that of linux, it must have made a change somewhere

• is there a way to provide default values for these variables ?

  I presume that init might have the default values and forked processes inherit the values & there is possible modification of values somewhere after forking (if someone knows the actual location of such code, please share)

• What is the purpose of each environment variable in list ?

  I understand the PATH & LD_LIBRARY_PATH variables, which are derived from linux. What about the others ? When are they used ? What would an Android app (possibly NDK) use them for ?

Thanks.

Answer 1

Android使用的是Linux，但它不是GNU / Linux，因此很多东西都不同。