execve grep process never exit - c

Question

The following code simulate the pipe and grep operation by forking process and using execve system call. The output seems fine, however, the grep process seems never exit (still running in the back) until the whole process ends. What's the problem? It is abnormal since using grep in shell always exit.
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <fcntl.h>
int main(int argc, char *argv[], char *env[]) {
char ch[32];
while (1) {
scanf("%s", ch);
int pd[2];
if (pipe(pd) == -1) {
perror("Pipe failed");
exit(1);
}
int childPid, pid;
if ((childPid = fork()) < 0) {
perror("fork failed\n");
exit(1);
} else {
// parent process
if (childPid) {
int status;
wait(&status);
// print exit code of child process
printf("Exit code %d\n", status);
}
// child process, execute command
else {
// fork a child
if ((pid = fork()) < 0) {
perror("fork failed\n");
exit(1);
}
if (pid) { // parent as pipe WRITER
close(pd[0]);
close(1);
// replace input with pipe
dup(pd[1]);
char* cmds[] = { "/bin/cat", "aa", 0 };
execve(cmds[0], cmds, env);
exit(0);
} else { // child as pipe READER
close(pd[1]);
close(0); // close its READ end
dup(pd[0]);
char* cmds[] = { "/bin/grep", "rw", 0 };
execve(cmds[0], cmds, env);
exit(0); // never been here
}
}
}
}
return 0;
}
Here is the output I monitor the process before and after running this program once.
hengstar#ubuntu:~$ ps -ef | grep "grep"
hengstar 58073 58038 0 01:43 pts/26 00:00:00 grep --color=auto grep
hengstar#ubuntu:~$ ps -ef | grep "grep"
hengstar 58075 1886 0 01:43 pts/11 00:00:00 /bin/grep drw
hengstar 58077 58038 0 01:43 pts/26 00:00:00 grep --color=auto grep

Answer 1

The exec family of functions never returns. Their purpose is to load a new program to replace the current program running in the process.
If an exec function returns, it means there was an error.

Answer 2

I laughted so hard I myself when I found this! Did you noticed that while(1) above? Well, everything is okay, except for that! Without it, your program works as you describe it to.
BTW: It happens that if a process's parent dies, the child becomes adopted by init, a.k.a (pid_t)1. That was happening with your code with while(1).