How can I stop the program inside the a parent or a child process? - process

Question

I have this piece of code that I developed just to address a problem that I have in another large program that I am developing.
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <cstring>
#include <cstdlib>
#include <sys/types.h>
#include <sys/wait.h>
#include <errno.h>
#include <limits.h>
#include <string>
#include <iostream>
using namespace std;
void processLine (char []);
void readLine(char []);
const int LIMIT = 512;
int main(int argc, char *argv[])
{
char oneLine[LINE_MAX];
readLine(oneLine);
return 0;
}
void readLine(char line[])
{
processLine(line);
//Otherstuff
------------
}
void processLine(char line[])
{
pid_t process;
int child_status;
string input;
cout << "Input: ";
cin >> input;
process = fork();
if(process == 0)
{ // do nothing
}
else
{
//parent
if(input == "quit")
{
printf("Quit command found ! \nExiting ");
for(int i = 0;i < 3;i++)
{
printf(".");
fflush(stdout);
sleep(1);
}
printf("\n");
exit(0);
}
else
{
wait(&child_status);
}
}
}
My goal is simple, When the user enter quit.
I will just display
Quit command found
Exiting ...
And there is a delay of one second between each of these three dots.
However the output that I get is
Quit command found
Exiting . other stuff ..
However, what seems to happen is that the parent process returns and then executes other stuff from the calling function before it continues to print the other two dots. How would I avoid the parent process from doing that ?

Answer 1

Use waitpid() like this:
pid_t childPid;
childPid = fork();
...
int returnStatus;
waitpid(childPid, &returnStatus, 0); // Parent process waits here for child to terminate.
Use it here
if(childPid == 0) // fork succeeded
{
// Do something
exit(0);
}
else // Main (parent) process after fork succeeds
{
int returnStatus;
waitpid(childPid, &returnStatus, 0);
}