Create a screencast of a terminal session using scriptreplay.

I recently ran into an issue where I needed to demo a project without actually being present for the demo. I thought about recording (into some video format) a screencast of my terminal window and then having my audience play it at the time of the demo. This would have worked just fine, but, as I was browsing the internet searching for exactly how to record a screencast of this nature, I ran across a blog post talking about how to play back terminal sessions using the output of the script program. This piqued my interest for several reasons:
  1. I have used script many times to log results of tests.
  2. This method of recording a shell session is much more efficient than recording it into video because it only stores the actual text of the output as well as some timing information.

In order to “record” using script you store the terminal output and the timing information to two different files using a command like the following:

script -t 2> screencast.timing screencast.log

The -t in the command causes script to output timing data to standard error. The 2> screencast.timing causes standard error to be redirected to the file screencast.timing. The screencast.log file will hold everything printed on the terminal during the course of the screencast session.

After running the command, execute a few programs (ls, echo "Hi Planet", etc…) and then type exit to end the session.

Now the screencast is stored in the two files. You can play back the screencast using:

scriptreplay screencast.timing screencast.log

And Voila. As long as your target audience has a box with script/scriptreplay installed then they can view your screencast!

I have included a screencast.timing and a screencast.log file you can download and use with scriptreplay if you would like to demo this out. The files combined are under 5K in size for a 1 minute 40 second screencast, however I think the actual size of the files depends more on how much data was output rather than the length of the screencast.

Even better than using my screencast, create one yourself!


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