Concurrency using fork in UNIX

#include <iostream.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

int main ( int argc, char **argv )
{
    int i, pid;

    pid = fork();

    cout << pid << endl;

    for ( i = 0; i < 5; i++) {
        cout << getpid() << ' ' << i << endl;
    }

    if ( pid ) wait(NULL);
}

• New process starts execution by returning from fork

• Child and parent are nearly identical
  parent gets the child process id from fork
  child gets 0 back from fork

• Parent should wait for child to exit