Signal Processing wifexited/wexitstatus/wifsignaled for C + + wait capture

When a process is normal or abnormally terminated, the kernel sends a SIGCHLD signal like its parent process because the child process is an asynchronous event, so this signal is also the asynchronous notification that the kernel sends to that parent process. The parent process can choose to ignore the signal or provide a function that is called to execute when the signal occurs. The system default action for this signal is to ignore it.

What happens to a process that calls wait or waitpid:

• If all of its child processes are running, it is blocked.
• If a child process has been terminated, the waiting parent process gets to the terminating state, then the terminating state of the child process is taken back immediately.
• If he does not have any child processes, an immediate error is returned.

Wifexited (status) is a non-0 value if the child process ends normally.
Wexitstatus (status) Gets the end code returned by the child process exit (), typically using wifexited to determine whether the macro ends properly before it can be used.
wifsignaled (status) This macro value is true if the child process ends because of a signal.
Wtermsig (status) Gets the signal code that the child process aborts because of the signal, generally uses wifsignaled to judge before using this macro.
wifstopped (status) This macro value is true if the child process is in a paused execution condition. This is generally the case only if you are using wuntraced.
Wstopsig (status) Gets the signal code that caused the child process to pause.

1     if(wifexited (status))2cout <<"normal termination, exitstatus ="<< wexitstatus (status) <<Endl;3     Else if(wifsignaled (status))4cout <<"abnormal termination, signalstatus ="<< wtermsig (status) <<Endl;5     Else if(wifstopped (status))6cout <<"Child stopped, signal number ="<< wstopsig (status) <<Endl;7     Else 8cout <<"Unknown Status:"<< status << Endl;