Which Unix/Linux system call creates a new process by duplicating the calling process?

Which Unix/Linux system call creates a new process by duplicating the calling process?

• A. Fork
• B. Exec
• C. Kill
• D. Wait

Answer: (A)

In Unix-like systems, the call that creates a new process by duplicating the calling process is fork. When you fork, the operating system makes a new process—the child—that is almost an exact copy of the parent at that moment. Both processes continue execution from right after the fork, but they have separate process contexts. The return value lets you tell them apart: the parent receives the child’s process ID, while the child receives zero. If something goes wrong, the call returns a negative value. This is different from the other system calls. Exec does not create a new process; it replaces the current process image with a new program. Kill sends a signal to one or more processes, not creating new ones. Wait makes the calling process pause until a child changes state (like finishing), again without creating anything new.

In Unix-like systems, the call that creates a new process by duplicating the calling process is fork. When you fork, the operating system makes a new process—the child—that is almost an exact copy of the parent at that moment. Both processes continue execution from right after the fork, but they have separate process contexts. The return value lets you tell them apart: the parent receives the child’s process ID, while the child receives zero. If something goes wrong, the call returns a negative value.

This is different from the other system calls. Exec does not create a new process; it replaces the current process image with a new program. Kill sends a signal to one or more processes, not creating new ones. Wait makes the calling process pause until a child changes state (like finishing), again without creating anything new.