In this case the quotes are not necessary, might be nice to inform the user of that (though this is how Bash works normally anyway).

server

• input validation: disallow control characters (any others we should disallow?)
• command execution timeout: prevent a denial-of-service attack or just an accidental overloading of resources. probably limit to ~10 sec
• user permissions: execute commands as user with no write permissions (also no read, if possible)
• run all commands inside a chroot; look into Python's os.chroot

client

• separate client-side code from server side
• tech upgrades: use webpack/create-react-app, upgrade to latest React, use functional components
• host frontend on AWS
• address other UI enhancements as desired

I am attempting to get the project to run on Ubuntu 16.04.04.

I installed npm using apt-get and followed the instructions in the README. At the step npm install && npm start I get an error.

watchify -v -o dist/bundle.js -t scssify -t reactify src/app.jsx

/usr/bin/env: ‘node’: No such file or directory

npm ERR! Linux 4.4.0-116-generic
npm ERR! argv "/usr/bin/nodejs" "/usr/bin/npm" "start"
npm ERR! node v4.2.6
npm ERR! npm  v3.5.2

I realise the project has not been touched in some time but I am eager to get it working as it's the only tool of it's kind I have been able to find.

For operations, with confirmation dialog.

Since diff is computationally expensive and calculated client-side, if the user's input is over some limit it might be nice to warn them with something like "You've entered a large input. If your browser is laggy, try disabling 'Show diff' for a smoother experience."

If I add a new grep operation, for example, grep will complain to stderr that its argument list is empty, an error will be returned to the frontend, and the Editor.state.outputs won't update.

We could fix this by pushing a blank output at the same time we push a blank operation.