CTRL+C will send a break (stop execution) when no text is selected. Try it ;-)

Reference

Did you try the following key combination: CTRL+C

UPDATE

For Windows 10 (cmd, PowerShell) you can use one of this:

• Right CTRL+C
• CTRL+Pause/Break

Ctrl + C should stop a program running from the command prompt, similar to Linux.

If that doesn't work try to force kill a process from the command prompt, using the following command:

taskkill /F /IM process.exe

/F will force termination of the process, and /IM means you're going to provide the running executable that you want to end, thus process.exe is the process to end.

Try to use Alt + F4.

The mechanism that cmd.exe uses¹ is GenerateConsoleCtrlEvent, and it is not available when your Process.Start call created a new console, because of this restriction in the documentation:

Only those processes in the group that share the same console as the calling process receive the signal. In other words, if a process in the group creates a new console, that process does not receive the signal, nor do its descendants.

The option you have is to not launch cmd.exe directly, but start a console program that is in turn responsible both for starting cmd.exe in its shared console, and also keeping a communication link with your program open in order to know when to generate console control events.

Actually it should be the console subsystem detecting Ctrl+C and generating the console event, and it's received by both cmd.exe and any child process. cmd.exe has a complex handler that will cancel a running builtin command (like dir) and not exit. Child processes may also have logic to exit cleanly and save state when the console control eventis seen.

Actually I can use start /wait command, it's the same as the above as it will wait for the file to execute but will open it in a different window, which I could easily close and force the program to restart without terminating my batch.

:start
start /wait C:\Squid\bin\squid.exe
timeout 1
goto start

Note: upon closing the batch may prompt to terminate execution. I found the way dealing with it here: https://superuser.com/questions/35698/how-to-supress-terminate-batch-job-y-n-confirmation

rem Bypass "Terminate Batch Job" prompt.
if "%~1"=="-FIXED_CTRL_C" (
   REM Remove the -FIXED_CTRL_C parameter
   SHIFT
) ELSE (
   REM Run the batch with <NUL and -FIXED_CTRL_C
   CALL <NUL %0 -FIXED_CTRL_C %*
   GOTO :EOF
)