Can I update the adb shell's environment variables?

Question

I wanted to update the PATH environment variable permanently in the adb shell. I guessed the shell was mksh for I've found /system/bin/sh pointing to /system/bin/mksh. Then I tried

• Making a new file /data/.mkshrc and adding the PATH definition into it.
• Copy the above file into /.
• Copy to /root.

But all attempts failed.

Answer 1

In addition to what Alex-p wrote, you can also set the ENV environment variable to override the path of the mkshrc file used.

All login shells also read /system/etc/profile and $HOME/.profile (these are a good place to export ENV). Apparently (for some reason that defies my ability to explain), adb shell does not start a login shell¹, though, so /system/etc/mkshrc is the file you will have to change for that.

(Disclaimer: I’m the mksh maintainer.)

① I’d expect “adb shell” to behave like ssh and start login shells if there is no explicit command given, as it does start a (new) session every time it’s run. Subshells will be interactive but not login shells, of course. But this is not the place to discuss that… if I care I’ll take it up at AOSP via Gerrit.

Answer 2

By default stock Android mksh uses this config file: /system/etc/mkshrc

Answer 3

To update the PATH variable inside a running adb shell you can use the expect command. This works on a non-rooted phone where you can't edit system files as suggested in the other answers.

Put the following script somewhere on the path of your development machine, for example in ~/bin/adb-shell-busybox:

#!/usr/bin/expect --
spawn adb shell
expect "$" {
    sleep 0.1
    send "export PATH=/data/data/burrows.apps.busybox/app_busybox/:\$PATH\n"
}
interact

You can also inject any other setup commands that you might need.