Gestão de processos fork (v 1.0.1)

// Apple Xcode


#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;
}