Lately I found myself launching scriptcs more and more to do simple calculations. I half-jokingly said on twitter that I’d better remap calc.exe to scriptcs.exe on my machine. However it seems that my joke tweet was taken seriously by some people, and I was asked how this was done. So here goes!

For this next trick I will use my most favorite Windows trick – the Image File Execution Options (IFEO). I’ve blogged about IFEO in the past, it’s generally used to allow attaching a debugger to a process before it starts, but can also do other useful things, such as replacing the Windows Task Manager with Process Explorer, or even disabling some processes launching, which is useful to prevent Narrator in Windows 8 from launching via the Win-Enter key.

So here is how to remap calc.exe to launch scriptcs instead. First, locate on your machine where scriptcs.exe is installed, as we need the full path. You can use the command where scriptcs.exe in CMD to find it. If you don’t have scriptcs.exe in path, best install it via Chocolatey (you’re welcome!)

1. Open the registry editor (regedit.exe), and navigate to:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options

2. Create a new key called calc.exe

3. Inside the newly created key, create a new String Value called Debugger

4. Double-click Debugger, and set c:\path\to\scriptcs.exe -repl as the value

That’s it, from now on when you launch calc.exe, scriptcs.exe will open instead! To undo this, simply delete the key calc.exe from the registry path above.

P.S. if you have Windows SDK installed, you can use the utility gflags.exe to do this instead:

1. Launch gflags.exe (need to be launched elevated)
2. Go to the Image File tab
3. In the Image text box, write calc.exe and press TAB (I know)
4. Down at the bottom, under Debugger, write c:\path\to\scriptcs.exe -repl and press OK

Bonus: now replace devenv.exe with scriptcs.exe!

Happy hacking!