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How do I use Waitpid and wait?

How do I use Waitpid and wait?

Either of wait or waitpid can be used to remove zombies. wait (and waitpid in it’s blocking form) temporarily suspends the execution of a parent process while a child process is running. Once the child has finished, the waiting parent is restarted.

How use Waitpid Linux?

General description

  1. If pid is greater than 0, waitpid() waits for termination of the specific child whose process ID is equal to pid.
  2. If pid is equal to zero, waitpid() waits for termination of any child whose process group ID is equal to that of the caller.
  3. If pid is -1, waitpid() waits for any child process to end.

What does wait () do?

The wait() function will suspend execution of the calling thread until status information for one of its terminated child processes is available, or until delivery of a signal whose action is either to execute a signal-catching function or to terminate the process.

What is Waitpid used for?

The waitpid() function allows the calling thread to obtain status information for one of its child processes. The calling thread suspends processing until status information is available for the specified child process, if the options argument is 0.

What is wait (& status?

The wait() system call suspends execution of the current process until one of its children terminates. The call wait(&status) is equivalent to: waitpid(-1, &status, 0); The waitpid() system call suspends execution of the current process until a child specified by pid argument has changed state.

What is Waitpid status?

What is wait Linux?

wait is an inbuilt command in the Linux shell. It waits for the process to change its state i.e. it waits for any running process to complete and returns the exit status.

How does wait function work?

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();

What is the difference between waitpid and wait?

waitpid is more flexible: If pid == -1, it waits for any child process. In this respect, waitpid is equivalent to wait. If pid > 0, it waits for the child whose process ID equals pid. If pid == 0, it waits for any child whose process group ID equals that of the calling process.

Why does waitpid () return 0?

If WNOHANG was given, and if there is at least one process (usually a child) whose status information is not available, waitpid () returns 0.

What is the use of waitid () system call?

The waitid () system call (available since Linux 2.6.9) provides more precise control over which child state changes to wait for. The idtype and id arguments select the child (ren) to wait for, as follows: Wait for the child whose process ID matches id. Wait for any child whose process group ID matches id. Wait for any child; id is ignored.

Where does wait () and waitpid () store status information?

If status is not NULL, wait () and waitpid () store status information in the int to which it points. This integer can be inspected with the following macros (which take the integer itself as an argument, not a pointer to it, as is done in wait () and waitpid ()!):