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Does child process run before parent?
The goal is to run the child process first. In short, the logic behind it is that if the child is ran first, the overhead of copy on write (COW) is eliminated if the child is calling exec since the parent does not have any chance to write to the address space. There is not really one executing before the other.
Why does parent wait for its child process?
A call to wait() blocks the calling process until one of its child processes exits or a signal is received. After child process terminates, parent continues its execution after wait system call instruction. It receives a signal (from the OS or another process) whose default action is to terminate.
What will happen if the parent terminates without calling wait ()?
What happens to zombie processes when its parent terminates. Assume that a process created multiple child processes and then didn’t use wait() system call. So, all child processes will become zombie after they terminate. Their PCB still exists in the main memory and they also do not have a parent.
What happens at the end of a child process?
End of life. When a child process terminates, some information is returned to the parent process. When a child process terminates before the parent has called wait, the kernel retains some information about the process, such as its exit status, to enable its parent to call wait later.
When does a process become a parent process?
Parent Process All the processes in operating system are created when a process executes the fork () system call except the startup process. The process that used the fork () system call is the parent process. In other words, a parent process is one that creates a child process.
What happens to the kernel when a child process terminates?
When a child process terminates, some information is returned to the parent process. When a child process terminates before the parent has called wait, the kernel retains some information about the process, such as its exit status, to enable its parent to call wait later.
How does a process end up without a parent?
Another way for a process to end up without a parent is if its parent dies, leaving an orphan process; but in this case it will shortly be adopted by init . The SIGCHLD signal is sent to the parent of a child process when it exits, is interrupted, or resumes after being interrupted.