Syntax of waitpid(): The value of pid can be: < -1: Wait for any child process whose process group ID is equal to the absolute value of pid. -1: Wait for any child process. 0: Wait for any child process whose process group ID is equal to that of the calling process. > 0: Wait for the child whose … Read more
If you pass -1 and WNOHANG, waitpid() will check if any zombie-children exist. If yes, one of them is reaped and its exit status returned. If not, either 0 is returned (if unterminated children exist) or -1 is returned (if not) and ERRNO is set to ECHILD (No child processes). This is useful if you want to find out if any of your children recently died without having … Read more