04.practical.work.fork.exec.c

#include <stdio.h>
#include <unistd.h>
#include <sys/wait.h>

int main(){
        int pid = fork();
        if (pid) {
                // you are parent
                printf("Main process, first child process has id: %d\n",pid);
                wait(NULL);
                printf("Finishing executed first child process!\n");
                pid = fork();
                if(pid) {
                        printf("Main process, second child process id: %d\n",pid);
                        wait(NULL);
                        printf("Finishing executed second child process!\n");
                }
                else if (pid == 0) {
                        // you are child 2
                        printf("child process 2 begin run:\n");
                        char *arg[]={"/bin/free","-h",NULL};
                        execvp(arg[0],arg);
                }
                else printf("error can not fork second child\n");
        }
        else if (pid == 0) {
                // you are child 1
                printf("child process 1 begin run:\n");
                char *arg[]={"/bin/ps","-ef",NULL};
                execvp(arg[0],arg);
        }
        else printf("error can not fork anything\n");
        return 0;
}