sending control+c (SIGINT) to NSPIPE in objective-c

Question

Hello, I am trying to terminate an openvpn task, spawned via NSTask.

My question:

Should I send ctrl+c (SIGINT) to the input NSPipe for my NSTask?

inputPipe = [NSPipe pipe]; 
taskInput = [inputPipe fileHandleForWriting];
NSString dataString = @"\cC";
[taskInput writeData:[dataString dataUsingEncoding: [NSString defaultCStringEncoding]]];

Alternatively, I was thinking about using kill( pid, SIGINT ); but it would be much more complicated since the process ID has to be determined via a detour ([task processIdentifier] does not help here) - the original NSTask calls:

/bin/bash -c sudo -S | mypassword ....

That's not nice, I know but it is only called once and the sudo password has been entered in that case already.

thanks for any suggestions/opinions/etc.

Ron

Answer 1

Control-C and SIGINT are not the same thing.

In the case of keyboard input, there's a "tty driver" in the OS that does things like echoing characters, processing delete keys, and so forth. It's also the thing that recognizes the control-C (or whatever your intr character is) and sends a SIGINT to the process.

When you have a pipe to another process, there's no tty driver involved*, so control-C is just passed through as ordinary data.

You will need to locate the pid and send a SIGINT directly to it. Of course, you might not actually have the permissions to do send it the signal (because you used sudo to run the other task as root)....

*unless you're using a pseudo-terminal (pty), which NSPipe doesn't and you don't want to do anyway :-)