UNIX for Dummies Questions & Answers

I have been having some trouble trying to get some code working, so I was wondering...what system calls are required to execute a different program from an already running process?

From a C programme?

If so, have a look at the man pages for these:

popen() if you need to send input to the command, or read output back from the command; be advised that with popen() you can only read or only write.

system() if you just need to execute a command. You'll get the exit code back, but no output.

fork() with exec() and possibly pipe() if you need absolute control over everything or need bidirectional communication with the child process.