当父进程调用exec命令时，子进程会发生什么情况

Question

Suppose we have a parent process and if it calls an exec function, after calling a fork to create child process.

Now what happens to the child process: will it act like the original parent process, such that the user won't spot the difference that the parent process got replaced with some other binary ?

I think this question differs from the following question what happens to child process? .

if ( (pid == fork ()) != 0 )
{
    if (strcmp(cmd,"mypwd")==0)
    {
        execlp (“mypwd”,0);
    }

    ...
    ...

    else if (strcmp(cmd,"myexit")==0)
        exit(1);
}

Answer 1

The pid of the parent process will remain the same after the exec , so the process hierarchy won't be affected.

The problem with this approach is that the newly replaced parent process generally won't be aware that it has previously spawned a child and will not call wait or waitpid on it. This will cause the child process to become a zombie when it exits.