record and replay interactive terminal sessions
Playitagainsam is a tool and a corresponding file format for recording and replaying interactive terminal sessions. It takes inspiration from the unix commands “script” and “ttyrec” and the python tool “playerpiano”.
Useful features include:
- ability to replay with fake typing for enhanced “interactivity”
- ability to replay synchronized output in multiple terminals
It’s early days, still kinda buggy and easy to crash. But I hope this will be resolved in short order!
Run the software using either the included “pias” script, or using the python module-running syntax of “python -m playitagainsam”.
Record a session like this:
$ pias record <output-file>
This will drop you into a shell and record all the input and output that occurs during the session. Once you exit the shell, all activity will be written into the output file as a JSON document.
Replay a recorded session like this:
$ pias play <input-file>
This will start a simulated playback of the original shell. Press any keys to type, and hit “enter” when you reach the end of a line.
Playitagainsam has some extra features that distinguish it from similar solutions.
It’s possible to record activity in several terminals simultaneously as part of a single session, which can be useful for e.g. demonstrating a server process in one terminal and a client process in another. Join a new terminal to an existing recording session like this:
$ pias --join record <output-file>
Choice of Manual or Automated Typing
While the default playback mode assumes interactive typing, it is also possible to have pias type automatically for you. You can have it enter individual commands but wait for you to manually trigger each newline like this:
$ pias play <input-file> --auto-type
Or you can have it automatically type all input like this:
$ pias play <input-file> --auto-type --auto-waypoint
These options both accept an integer millisecond value which will control the speed of the automated typing.
Canned Replay or Live Replay?
The default playback mode outputs back the ‘canned’ output text from the original terminal session(s), without any side effects. However, the side effects might be desirable during the presentation.
For instance, when demoing a REST API, the presenter might want to show the effects of the API calls on a service using a browser. Or the demoed code could drive some other non-console output, like a visualisation or a game.
The –live-replay option connects the prerecorded input to a live shell for actual live output and side effects:
$ pias play <input-file> –live-replay
This option is composable with the previous ones:
$ pias play <input-file> –live-replay –auto-type –auto-waypoint
Live replay also works two or more joined terminal sessions.
And an example presentation using this code is at:
Getting this all running just right can be tricky business! Here’s some thing that you should be aware of:
- All terminals should be using utf8 encoding, or you’ll see strange output and probably some outright errors.
- All terminals in a session should be the same size. This restriction may go away in the future.
- The live-replay option has its own particularities:
- Sessions created with the –append switch won’t continue after the first recording session ends.
- Sometimes keypresses “bounce”, and double characters get inserted.
- Some live-replay output sequences lasting longer than the corresponding output in the recording session can get buffered waiting for the next user action.