I am trying to extend the functionality of my custom unix shell which I earlier wrote as part of my lab assignment. It currently supports all commands through execvp calls, in-built commands like pwd, cd, history, echo and export, and also redirection and pipes. Now I wanted to add the support for running a command in background e.g. $ls -la& Now I also want to implement bg and fg job control commands.

I know this can be achieved if I execute the command by forking a new child process and not waiting for it in the parent process. But how do I again bring this command to foreground using fg? I have the idea of entering each background command in a list assigning each of them a serial number. But I don't know how do I make the processes execute in the background, then bring them back to foreground. I guess wait() and waitpid() system calls would come handy but I am not that comfortable with them. I tried reading the man pages but still am in the dark. Can someone please explain in a layman's language how to achieve this in UNIX system programming? And does it have something to do with SIGCONT and SIGSTP signals?