What is the use of Waitpid system call?

What is the use of Waitpid system call?

The waitpid() system call suspends execution of the current process until a child specified by pid argument has changed state. By default, waitpid() waits only for terminated children, but this behaviour is modifiable via the options argument, as described below.

Which system call function is used to allow a process to wait for a specific child to terminate?

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. Child process may terminate due to any of these: It calls exit();

How does Waitpid work?

If pid is greater than 0, waitpid() waits for termination of the specific child whose process ID is equal to pid. If pid is equal to zero, waitpid() waits for termination of any child whose process group ID is equal to that of the caller.

Which system call creates a child process?

Fork system call
Fork system call is used for creating a new process, which is called child process, which runs concurrently with the process that makes the fork() call (parent process). After a new child process is created, both processes will execute the next instruction following the fork() system call.

What happens when a process terminates but its parent does not wait for it?

Zombie process is that process which has terminated but whose process control block has not been cleaned up from main memory because the parent process was not waiting for the child.

When to use waitpid on a child process?

If pid is -1, waitpid () waits for any child process to end. If pid is less than -1, waitpid () waits for the termination of any child whose process group ID is equal to the absolute value of pid. Points to a location where waitpid () can store a status value. This status value is zero if the child process explicitly returns zero status.

How does waitpid ( ) work in a system call?

The waitpid () system call suspends execution of the current process until a child specified by pid argument has changed state. By default, waitpid () waits only for terminated children, but this behaviour is modifiable via the options argument, as described below.

What happens to parent process after wait system call?

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. If any process has more than one child processes, then after calling wait (), parent process has to be in wait state if no child terminates.

How does the wait system work in C?

Syntax in c language: If any process has more than one child processes, then after calling wait (), parent process has to be in wait state if no child terminates. If only one child process is terminated, then return a wait () returns process ID of the terminated child process.