Difference between "system" and "exec" in Linux?

system() calls out to sh to handle your command line, so you can get wildcard expansion, etc. exec() and its friends replace the current process image with a new process image.

With system(), your program continues running and you get back some status about the external command you called. With exec(), your process is obliterated.

In general, I guess you could think of system() as a higher-level interface. You could duplicate its functionality yourself using some combination fork(), exec(), and wait().

To answer your final question, system() causes a child process to be created, and the exec() family do not. You would need to use fork() for that.

The exec function replace the currently running process image when successful, no child is created (unless you do that yourself previously with fork()). The system() function does fork a child process and returns when the command supplied is finished executing or an error occurs.

system() will execute the supplied command in a child process that it spawns. exec() will replace the current process with the invocation of the new executable that you specify. If you want to spawn a child process using exec, you'll have to fork() your process beforehand.