Adjust volume with Android Terminal Emulator command?
Use the following commands to change the volume from Android Terminal emulator (or other terminal emulator apps):

Volume Up:

input keyevent 24


Volume Down:

input keyevent 25


In case pressing the volume key once shows the current volume, you can input the command twice to increase/decrease the volume 

input keyevent 25; input keyevent 25


Toggle Mute/Unmute

input keyevent 164