firefox proxy settings via command line

Question

How do I change Firefox Proxy settings via command line on windows xp/2k?

Thanks

Answer 1

user.js is better for customizations as you can include only the lines you want to manipulate, i.e. instead of find-replace you can just overwrite the entire file. Also, prefs.js (at least on Firefox 65.0.1 for Mac) starts with a warning:

// DO NOT EDIT THIS FILE.
//
// If you make changes to this file while the application is running,
// the changes will be overwritten when the application exits.
//
// To change a preference value, you can either:
// - modify it via the UI (e.g. via about:config in the browser); or
// - set it within a user.js file in your profile.

In my case, user.js didn't exist, so I created it and included the line to switch between "No proxy" and "Manual proxy configuration" (I'm using only one SOCKS proxy all the time, so no need to change port number or any other details, just flip 0 to 1 in the following line):

user_pref("network.proxy.type", 1);

I ended up with a bash script that I placed at /usr/local/bin/firefox:

#!/bin/bash
if [ $# -eq 0 ]; then
  echo 'user_pref("network.proxy.type", 0);' > ~/Library/Application\ Support/Firefox/Profiles/t5rvw47o.default/user.js
  open -a Firefox
else
  case $1 in
    vpn)
      echo 'user_pref("network.proxy.type", 1);' > ~/Library/Application\ Support/Firefox/Profiles/t5rvw47o.default/user.js
      open -a Firefox
  esac 
fi

To use it, I make sure no Firefox is running and then run firefox to have a straight connection and firefox vpn to use proxy.