Untitled

// apple xcode
// paulogp
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>

void func_simula_processamento();

int main (int argc, const char * argv[])
{
        int the_fork, the_status;

        // function shall create a new process
        // the new process (child process) shall be an exact copy of the
        // calling process (parent process)
        the_fork = fork();

        // getppid: shall return the parent process ID of the calling process
        printf("pid = %d, ppid = %d\n", getpid(), getppid());

        // waits for seconds or until a signal is delivered, whichever happens first
        sleep(1);

        // seed random number generator
        // 'srandom' call only needs to be done once per program
        srandom(getpid());

        char *ptr = malloc(8);
        strcpy(ptr, "pai\n");

        // the_fork == 0: == "filho": termina no exit(1)
        // apenas o filho realiza esta accao
        // as variaveis dentro deste filho nao afectam o pai ou outros filhos
        if (the_fork == 0)
        {
                // pretende demonstrar que a var alterada pelo filho nao afecta o pai
                strcpy(ptr, "filho\n");
                fwrite(ptr, 8, 1, stdout);

                // flush a stream: forca saida dos valores
                fflush(stdout);

                // a accao do filho termina aqui
                // o filho morre neste ponto
                exit(1);
        }

        // The waitpid() system call suspends execution of the calling process until a
        // child specified by pid argument has changed state.  By default, waitpid()
        // waits only for terminated children, but this behavior is modifiable via the
        // options argument
        the_fork = waitpid(the_fork, &the_status, 0);

        fwrite(ptr, 8, 1, stdout);

        printf("\n");

        // WIFEXITED: this macro queries the child termination status provided
        // by the wait and waitpid functions, and determines whether the child
        // process ended normally
        if (WIFEXITED(the_status))
                printf("valor de retorno de (%d): %d\n", the_fork, WEXITSTATUS(the_status));
        else
                printf("filho (%d) terminou de forma anormal\n", the_fork);

        return 0;
}