Question

I can open a program in terminal using:

stringstream s;
s<<"./~/rajat/app -parameter";
system(s.str().c_str());

My app keeps on running in a terminal , what I want to do is shut down this app from inside the same program and open it again using new parameters. How to do this?

Answer 1

You can’t do this using system. From (BSD) man 3 system:

The calling process waits for the shell to finish executing the command, ignoring SIGINT and SIGQUIT, and blocking SIGCHLD.

So your app will block until the completion or termination of the launched program.

You can get the behavior that you want by instead launching your program using fork/exec – man pages here, and here. This is what system is doing under the hood. You’ll launch the sub-process and maintain control in your app.

Using fork, you’ll get a process id for your launched process, and using that you can e.g. terminate the program using kill – man page here – and re-launch the program.

Look around for fork/exec examples, there are probably more than a few on this site.