What does Waitpid mean?
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 is the status in Waitpid?
Only one status is returned per waitpid function call. If pid is equal to -1, status is requested for any child process. If status information is available for two or more processes, the order in which their status is reported is not specified. If pid is greater than 0, status is requested for a single process.
How do you check the status of the child process?
You can get the exit status of the child via the first argument of wait() , or the second argument of waitpid() , and then using the macros WIFEXITED and WEXITSTATUS with it. waitpid() will block until the process with the supplied process ID exits.
What are Waitpid options?
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.
How does Waitpid work?
Suspends the calling process until a child process ends or is stopped. More precisely, waitpid() suspends the calling process until the system gets status information on the child. If the system already has status information on an appropriate child when waitpid() is called, waitpid() returns immediately.
Does Waitpid return anything?
RETURN VALUES If waitpid() returns because the status of a child process is available, it returns a value equal to the process ID of the child process for which status is reported.
What does Waitpid do in C?
More precisely, waitpid() suspends the calling process until the system gets status information on the child. If the system already has status information on an appropriate child when waitpid() is called, waitpid() returns immediately.
What does Waitpid return?
If waitpid() returns because the status of a child process is available, it returns a value equal to the process ID of the child process for which status is reported.
What is the difference between wait () and waitpid ()?
wait() and waitpid() The wait() system call suspends execution of the calling thread until one of its children terminates. The call wait(&wstatus) is equivalent to: waitpid(-1, &wstatus, 0); The waitpid() system call suspends execution of the calling thread until a child specified by pid argument has changed state.
Can Waitpid fail?
The waitpid() function shall fail if: ECHILD. The process specified by pid does not exist or is not a child of the calling process, or the process group specified by pid does not exist or does not have any member process that is a child of the calling process. EINTR.
Why is Waitpid useful?
It blocks the calling process until a nominated child process exits (or makes some other transition such as being stopped.) Typically you will use waitpid rather than generic wait when you may have more than one process and only care about one.
What is difference between wait and Waitpid?
wait(): on success, returns the process ID of the terminated child; on failure, -1 is returned. waitpid(): on success, returns the process ID of the child whose state has changed; if WNOHANG was specified and one or more child(ren) specified by pid exist, but have not yet changed state, then 0 is returned.
What does waitpid ( 1, status, status ) do?
waitpid (-1, &status, 0); The waitpid () system call suspends execution of the calling process until a child specified by pid argument has changed state. By default, waitpid () waits only for terminated children, but this behavior is modifiable via the options argument, as described below. The value of pid can be:
What happens when you call waitpid and wnohang?
Normally, a call to waitpid causes the calling process to be blocked until status information from the specified process is available; the WNOHANG option prevents the calling process from being blocked.
Which is the equivalent of the call waitpid ( )?
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. By default, waitpid () waits only for terminated children, but this behaviour is modifiable via the options argument, as described below.
What happens when a call to waitpid is blocked?
Normally, a call to waitpid causes the calling process to be blocked until status information from the specified process is available; the WNOHANG option prevents the calling process from being blocked. If status information is not available, waitpid returns a 0 .