处理 C 语言中的进程

Question

我在尝试处理从父亲进程发送到孩子所有进程的SIGUSR1信号时遇到问题。孩子的处理程序什么都不做。我检查了 kill 命令的结果，它返回 0，这意味着发送的消息正常。谁能帮忙？下面是子进程的代码。我使用 execl 将孩子代码与父亲区分开来。请注意，处理程序适用于警报调用

#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
#include <string.h>
/*Global declerations*/
int alarmflag=0;
double result=0;
int fd[2];
/*Handler for the alarm and SIGUSR1 signal*/
void signal_handler (int sig)
{
printf("******************");
if(sig==SIGALRM)
{
printf("Im child with pid:%d im going to die my value is %lf n",getpid(),result);
alarmflag=1;
}
if(sig==SIGUSR1)
{
printf("gotit!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!n");
}
}

double p_calculation ()
{
 int i=2;
 result=3;
 double prosimo=-1;
 while(!alarmflag)
    {
 prosimo=prosimo*(-1);
 result=result+(prosimo*(4/((double)i*((double)i+1)*((double)i+2))));
 i=i+2;
    }
}
main(int argc,char *argv[])
{
int fd[2];
/*handling signals*/
signal(SIGALRM,signal_handler);
signal(SIGUSR1,signal_handler);
/*Notify for execution time*/
printf("PID : %d with PPID : %d executing for %d seconds n",getpid(),getppid(),atoi(argv[1]));
/*end this after the value passed as argument*/
alarm(atoi(argv[1]));
p_calculation();
/*Notify for finish*/
printf("Done!!!n");
}

父亲的守则如下：

#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
#include <sys/types.h>
pid_t *childs; //array for storing childs pids
int number_of_childs;//variable for the number of childs
int count_controls=0;
/*Handler for the SIGINT signal*/
void control_handler(int sig)
{
int j;
for (j=0;j<number_of_childs;j++)
    {
    kill(childs[j],SIGUSR1);
    }
}
main (int argc,char *argv[]){
int i,child_status;
int fd[2];
char cast[512];
int pid;
number_of_childs=atoi(argv[1]);
signal(SIGINT,control_handler);
childs=malloc(number_of_childs*sizeof (pid_t));
if(pipe(fd)==-1)
    {
    perror("pipe");exit(1);
    }
for (i=0;i<number_of_childs;i++){
pid=fork();
    /*Create pipes to communicate with all children*/

    /*Fathers code goes here*/
    if(pid!=0)
        {
        printf("Parent process: PID= %d,PPID=%d, CPID=%d n",getpid(),getppid(),pid);
        childs[i]=pid; // Keep all your childs in an array
        printf("Child:%dn",childs[i]); 
        }
    /*If you are a child*/
        else 
        {
        /*Change the code for the childs and set the time of execution*/
        sprintf(cast,"%d",i+1);
        execl("./Child.out","",cast,NULL);
        }
    }   
        /*Father should never terminate*/               
        while (1);

}

Answer 1

当我从外壳中杀死孩子时，我看不到孩子有问题：

test]$ ./a.out 120
PID : 7406 with PPID : 7035 executing for 120 seconds 
******************gotit!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
******************Im child with pid:7406 im going to die my value is -nan 
Done!!!

父母被INT杀死确实会杀死USR1的孩子：

test]$ ./a.out 1 30
Parent process: PID= 7490,PPID=7035, CPID=7491 
Child:7491
PID : 7491 with PPID : 7490 executing for 40 seconds 
******************gotit!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

我的问题是当我对父亲进程使用 control -c 时。它得到 中断但来自处理程序的消息，即子项已收到 消息未显示 – Giannos 9 分钟前

问题是你在子过程中得到了SIGINT。尝试在子项中添加 SIGINT 处理程序，然后运行测试。

您可以看到按 ctrl-c 后当前实现会发生什么情况：

serge    7685  7035 99 08:01 pts/3    00:00:08 ./a.out 1
serge    7686  7685 30 08:01 pts/3    00:00:02 [Child.out] <defunct>

您的子进程获得 SIGINT 并终止。此外，有必要在父级中处理 SIGCLD，以摆脱处于失效状态的所有子进程：

if (sig == SIGCLD)
{
   // harvest terminated DEFUNCT child process
   pid = waitpid(-1, &status, WNOHANG);
}