What is Wnohang?
WNOHANG. This flag specifies that waitpid should return immediately instead of waiting, if there is no child process ready to be noticed. WUNTRACED. This flag specifies that waitpid should report the status of any child processes that have been stopped as well as those that have terminated.
What does Waitpid mean?
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 does Wnohang do in Waitpid?
That’s what WNOHANG is for. It prevents wait()/waitpid() from blocking so that your process can go on with other tasks. If a child died, its pid will be returned by wait()/waitpid() and your process can act on that.
How does wait pid work?
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.
How do I use getpid in Linux?
getpid() returns the process ID (PID) of the calling process. (This is often used by routines that generate unique temporary filenames.) getppid() returns the process ID of the parent of the calling process.
What does Waitpid wait for?
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 wait and Waitpid?
Wait() is a blocking call whereas waipid() can be made non-blocking with WNOHANG option. Wait() waits for any child process but waitpid() waits for a specific child equal to pid. By default waitpid() waits for the only terminated child where as wait() waits for both terminated or a signaled child.
Is Waitpid better than 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 any child whose process group ID equals that of the calling process.
Does Waitpid block?
waitpid can be either blocking or non-blocking: If options is 0, then it is blocking.
What is Wifexited return?
WIFEXITED and WEXITSTATUS are two of the options which can be used to know the exit status of the child. WIFEXITED(status) : returns true if the child terminated normally. WEXITSTATUS(status) : returns the exit status of the child. This macro should be employed only if WIFEXITED returned true.