c - 如何使多个子进程暂停直到发送信号

Question

我有一个程序，其中三个子进程都执行完全相同的操作，第四个子进程告诉发送信号，而主函数则等待三个子进程完成。我使用警报信号和两个用户信号来使子进程将输出发送到不同的终端。我使用暂停功能来等待信号，但是当我启动程序时，它就完成了，根本不等待。我是否正确使用了暂停？

int alarmR =0;
int SNMPR =0;
int reconR=0;
int child_pid[4];
char strD[100];
FILE *fpt[4];


void Alarmhandler(int sig);
void Reconfigure(int sig);
void SNMPhandler(int sig);
int which(int wait_ret, int child_proc[], int p);
void IT1(void);
void IT2(void);
void IT3(void);
void command(void);


void command(void)
{
    signal(SIGALRM,Alarmhandler);
        signal(SIGUSR1,Reconfigure  );
        signal(SIGUSR2,SNMPhandler  );

        char text;
        int n;
        printf("please enter a command from the following list\n");
        printf("\tsn:Send a SNMP request\n\trn:Send a reconfiguration");
        printf("script\n\tkn: shutdown process\n");
        scanf("%c%d",&text,&n);
        if(text == 'k')
        {
            printf("Terminated IT service %d\n",n);
            n = n-1;
            kill(child_pid[n],1);
        }
        else if(text=='s')
        {
            n = n-1;
            kill(child_pid[n],SIGUSR2);
        }
        else if(text=='r')
        {
            n = n-1;
            kill(child_pid[n],SIGUSR1);
        }

}   

void Alarmhandler(int sig)
{

    alarmR =1;

}

void Reconfigure(int sig)
{
    reconR =1;
}

void SNMPhandler(int sig)
{
    SNMPR =1;
}


int which(int wait_ret, int child_proc[], int p)
{
    int i;
    for (i = 0; i < p; i++)
        if (child_proc[i] == wait_ret)
            return i;
    return -1;
}




int main(int argc, char *argv[])
{
    int ttyindex;
//  int Terminal[4];
    int term_cnt = 0;
    int wait_r,x;
    int process = 0;
    int child_proc[4];
    int es[3];


    if(argc != 5) {
        printf("Usage: ./lab7 1 2 3 4\n");
        exit(1);
    }
    for(term_cnt =0; term_cnt <4;term_cnt ++)
    {
        ttyindex = -1;
        ttyindex = atoi(argv[term_cnt+1]);
        if (ttyindex < 1) {
             printf("invalid terminal number %s\n", argv[term_cnt+1]);
                exit(1);
        }
        sprintf(strD, "/dev/pts/%d", ttyindex);
    child_proc[process] = fork();
        if (child_proc[process] != 0) 
    {
        // parent process
        process++;
        child_proc[process] = fork();
        if (child_proc[process] != 0) 
        {
            // parent process
            process++;
                child_proc[process] = fork();
                if (child_proc[process] != 0) 
            {
                // parent process
                    process++;
                child_proc[process] = fork();
                if(child_proc[process] !=0)
                {
                        wait_r = wait(NULL);
                             x =which(wait_r, child_proc, process);

                        printf("Waited for %d (child %d) to finish.\n", wait_r,x);
                    if(WIFEXITED(wait_r))
                    {
                        es[x] = WEXITSTATUS(wait_r);
                    }

                        wait_r = wait(NULL);
                             x =which(wait_r, child_proc, process);

                        printf("Waited for %d (child %d) to finish.\n", wait_r,x);
                    if(WIFEXITED(wait_r))
                    {
                         es[x] = WEXITSTATUS(wait_r);
                    }

                        wait_r = wait(NULL);
                             x =which(wait_r, child_proc, process);

                        printf("Waited for %d (child %d) to finish.\n", wait_r,x);

                    if(WIFEXITED(wait_r))
                    {
                         es[x] = WEXITSTATUS(wait_r);
                    }
                    for(x = 0; x <3;x++)
                    {
                        if(es[x] == 0)
                        {
                            printf("\nJob well done IT specialist %d",(x+1));
                            printf(" Prepare for new attacks!\n");
                        }
                        else if(es[x] == 1)
                        {
                            printf("\nIT service %d compromised",(x+1));
                            printf(" , we are going out of business!\n");
                        }
                        else
                        {
                            printf("\nCall HR, we need a new");
                            printf(" cybersecurity expert for service");
                            printf(" %d\n",(x+1));
                        }
                    }


                }
                else
                {
                    child_pid[3] = getpid();
                    command();
                }
                } 
            else 
            {
                child_pid[2]=getpid();
                IT3();
            }
         } 
        else
        {
            child_pid[1] = getpid();
            IT2();
        }
     } 
    else
    {
        child_pid[0] = getpid();
        IT1();

    }

}


void IT1(void)
{
    printf("i live");
    signal(SIGALRM,Alarmhandler);
    signal(SIGUSR1,Reconfigure  );
    signal(SIGUSR2,SNMPhandler  );
    clock_t start=0, end=0;
    static int check = 0;
    static int recona =0;
    double t= 0;
    int threat= 1;
    srand48(time(NULL));
    fprintf(fpt[1],"This is IT service 1\n");
    while(1)
    {
        printf("%d  %d   %d",reconR,alarmR,SNMPR);
        pause();
    //  alarm(1);
        if(reconR == 1)
        {
            reconR =0;
            if(recona >0)
            {
                fprintf(fpt[1],"Cannot reconfigure more than once.you are fired!");
                exit(1);
            }
            if(threat < 16)
            {
                fprintf(fpt[1],"Threat level is not critical.you are fired");
                exit(1);
            }
            fprintf(fpt[1],"Reconfiguring system to thwart attack-this may take a few seconds\n");
            recona++;
        }
        if(alarmR == 1 )
        {
            if(check >0)
            {
                t =((double)(end - start))/CLOCKS_PER_SEC;
            }

            alarmR = 0;
            if(recona >0)
            {
                threat --;
            }
            else
            {
                if (drand48() < 0.5) 
                {
                    threat++;
                } 
                else if (threat > 1 && drand48() < 0.6) 
                {
                    threat--;
                }
            }
            if(t <5)
            {
                fprintf(fpt[1],"Next report available in %f seconds\n",(5-t));
            }
            if(threat >15)
            {
                fprintf(fpt[1],"Intruder! Data stolen...");
                exit(1);
            }
            else if(threat < 10 && recona >0)
            {
                fprintf(fpt[1],"Attack averted. Mission Complete");
                exit(0);
            }

        }
        if(SNMPR == 1)
        {
            if(check == 2)
            {
                end = clock();
                t = ((double)(end - start))/CLOCKS_PER_SEC;
            }

            SNMPR = 0;
            check = 1;
            if(t <5)
            {
                fprintf(fpt[1],"Load to high. Threat is increased");
                threat++;
                t = 0;
            }
            else{
                if(threat >=10)
                    fprintf(fpt[1],"Threat level is red\n");
                else if(threat <10 && threat >=5)
                    fprintf(fpt[1],"Threat level is orange\n");
                else
                    fprintf(fpt[1],"Threat level is green\n");
            }
            if(check ==1)
            {
                start = clock();
                check = 2;
            }


        }
    }


}

Answer 1

您可以使用 sigsuspend() 系统调用让进程等待信号，并使用kill() 向进程或进程组发送信号。我希望通过使用这两个系统调用，您可以编写您想要的代码任务。