about fork and execve system call

Question

It is said that fork system call creates a clone of the calling process, and then (usually) the child process issues execve system call to change its i

Answer 1

The "exec" family of functions replace the current process image(from where it is called) with a new process image, so the calling image is replaced by the new process image. For eg. if you were to run the 'ls' command from a shell(/bin/sh or /bin/csh) then the shell would fork to a new process which would then execute ls. Once the ls command exits it returns control to the parent process, which in this example is the shell.

If there were no fork functionality then the shell would be replaced by the 'ls' process which upon exit would leave you with an inaccessible terminal since the shell's image in memory was replaced upon the exec call to ls.

For variations in the 'exec' family look at 0x6adb015's answer.