Android - How to print tasks activity stack in terminal (backstack)

Use adb shell (in a terminal, go in <android-sdk-folder>/platform-tools).

To print a bunch of useful information:

./adb shell dumpsys activity -package 

To print only activities:

./adb shell dumpsys activity -package <your.package.name> | grep 'ACTIVITY'

To print only activities and their fragments:

./adb shell dumpsys activity -package <your.package.name> | grep -E 'ACTIVITY|Active Fragments|#[0-9]:|Added Fragments|Back Stack'