I have seen many softwares such as Update Manager and Synaptic Package Manager, they wait if some other program is using the /var/lib/dpkg/lock and is locked. How can we do this through the Terminal? I saw apt-get's manual but didn't find anything useful.
You can use the aptdcon command 
to queue up package manager tasks by communicating with aptdaemon instead of using apt-get directly.
So basically you can just do sudo aptdcon --install chromium-browser or whatever and while that command is running you can run it again but install different packages and apt-daemon will just queue them up instead of erroring out.
This is especially useful if you're doing a long upgrade or something and want to keep installing packages or if you're scripting something together and want to make sure installing things will be more reliable.
