Blocking process functions wait () and Waitpid ()

1. Wait () and waitpid () function descriptions

Wait ()

Once the process has called wait (), it immediately blocks itself, and the wait automatically parses whether a child process with the current process has exited, and if it finds a child process that has become a zombie, wait collects the child process information and destroys it and returns it. If no such child process is found , wait is blocked here until a child process finishes or the process receives a specified signal.

Waitpid ()

Waitpid () acts like Wait (), but it does not have to wait for the first terminating subprocess, and it has several options, such as providing a non-blocking version of the Wait () feature. In fact, the wait () function is just a special case of the Waitpid () function, and the Waitpid () function is called directly when implementing the Wait () function inside Linux.
The wait () function is implemented:

Static inline pid_t wait (int *wait_stat)

{

　　Return Waitpid ( -1,wait_stat,0);

}

2. Wait () and waitpid () function format description

(1) The Wait () function is formatted as follows:

(2) the Waitpid () function is formatted as follows

Blocking process functions wait () and Waitpid ()