By Greg Rowe | July 30, 2018

Over the years I’ve spent thousands of hours working with devices connected via serial ports. Only recently did I learn that the wonderful GNU screen can be used as a terminal emulator. screen has long been popular in the world of systems administration but rarely do have I seen it used in the context of software development.


In the Windows world, years ago, TeraTerm was a popular choice among knowledgeable developers. It offered a lot more than the standard Hyper Terminal application that shipped with MS Windows. Then again almost any terminal emulator worked better than Hyper Terminal. In more recent times putty, the highly capable ssh client for Windows gained popularity as a terminal emulator. Putty has become so popular that I’ve even seen developers run it on Linux for the sole reason that they could master a single tool for both Linux and Windows. If, however, you are primarily working on Linux then I recommend the use of GNU screen.

At first screen can be frustrating. You’ll probably find yourself asking things like “why isn’t ctrl-a working?” and “how do I exit this?!“. If you are patient and work through the initial learning curve you’ll reap rewards.


Launching screen as a terminal emulator is as easy as directing it to your serial port and telling it which baud rate to use. The example below is for a USB serial adapter.

screen /dev/ttyUSB0 115200

Escape Sequence

If you are an emacs user or accustomed to bourne shells you’ll very quickly become frustrated. screen uses ctrl-a as an escape sequence for sending commands to screen itself rather than the end terminal. This conflicts with default emacs keybindings for ‘beginning of line’ which is also the default binding for ‘beginning of line’ in a bourne shell or readline based application. You can either get used to this or rebind the key to something else. I opt to rebind the sequence since emacs keybindings are permanently burned into my brain.

To rebind edit ~/.screenrc with a new sequence. The sequence I chose is alt-shift-6 as it will not conflict with emacs.

# Make the escape sequence c-s-6
escape ^^^


I will not attempt to provide a screen tutorial since there are many tutorials that do a far better job. Instead I will provide the key commands you’ll need to know and let you find your own journey in learning screen in as much or as little detail as you desire.


At some point you’re going to want to exit screen. To exit use ESCAPE \ where ESCAPE is whatever sequence you chose for screen. In my case ctrl-shift-6 \ exits screen.


Inevitably you will want to look at output that scrolled past the active window. Using the scroll bars will not work as you expect. This is because screen keeps its own scroll back buffer. To scroll back and (optionally) copy text use ESCAPE esc. In my case that is ctrl-shift-6 esc. You can then use your cursor keys to navigate the history from the session.


One of the best features of screen is that you do not have to quit the application. You can detach from a session and reattach at a later time. A common case for this is doing work at your desk and then continuing your debug session in a lab or at home. To detach press ESCAPE d. In my case that is ctrl-shift-6 d.


With just a few commands you can be productive with screen as a terminal emulator.

  • launch - screen /dev/ttyUSB0 115200
  • quit - ESCAPE \
  • detach - ESCAPE d
  • scroll - ESCAPE esc
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