I do understand that while exec() does not return after it executes in Unix ,system() may or may not return depending on the situation.But can anyone explain why exec() system call does not return and also the differences between exec() and system() in Unix operating system
system() is equivalent to fork() + exec() + wait(); this means when a process run system() function it creates a new process and waits the end of this process. The new process executes the command in it's own environment, when it has finished the caller receives the signal child.
For further information
"exec replaces the current process image with a new process image", this means when it exits the caller exits too as the caller has become the new process.