C ++通过exec函数杀死子进程（而不是父进程）和正常运行时间

Question

I don't know if the current way I am killing the child processes is correct. I want when child three's timer (temp) hit's zero that it kills all the children, then the parent prints a message than exits. Also, I tried using sysinfo to get the uptime in child 2, but the sysinfo struct doesn't have uptime as a member in the environment I am running the program in. So, how do I use a exec function to get uptime from /usr/bin/uptime. Also, don't tell me to split everything up out of the main function because I am going to do that after I figure out how to complete the functionality.

The Code:

#include <string>
#include <ctime>
#include <iostream>
#include <sys/sysinfo.h>
#include <cstdlib>
#include <unistd.h>
#include <sched.h>
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <errno.h>

using namespace std;

pid_t parent_pid;

void sigquit_handler (int sig) {
assert(sig == SIGQUIT);
pid_t self = getpid();
if (parent_pid != self) _exit(0);
}

int main (string input) {
if (input.empty()) {
    input = "10";
}
signal(SIGQUIT, sigquit_handler);
parent_pid = getpid();
int number = atoi(input.c_str());
pid_t pid;
int i;
FILE* fp;
double uptime;

for(i = 0; i < 3; i++) {
    pid = fork();
    if(pid < 0) {
        printf("Error");
        exit(1);
    }
    else if (pid == 0) {
        if (i == 0) { //Child 1
            sleep(1);
            time_t t = time(0);   // get time now
            struct tm * now = localtime( & t );
            cout << (now->tm_year + 1900) << '-'
                    << (now->tm_mon + 1) << '-'
                    <<  now->tm_mday
                    << endl;
        }
        else if (i == 1) { //Child 2
            sleep(5);
            struct sysinfo info;
            cout << info.uptime << endl;
        }
        else { //Child 3
            int temp = number;
            int minute = temp / 60;
            int second = temp - (minute * 60);
            sleep(1);
            cout << minute << ":" << second << endl;
            temp--;
            if (temp == 0) {
                kill(-parent_pid, SIGQUIT);
            }
        }
    }
    else  {
            cout << "Program is Complete";
    }
}
}

Answer 1

Also, I tried using sysinfo to get the uptime in child 2, but the sysinfo struct doesn't have uptime as a member in the environment I am running the program in. So, how do I use a exec function to get uptime from /usr/bin/uptime

You can just set an alarm in a process and receive SIGALRM when the time has run out.

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I want when child three's timer (temp) hit's zero that it kills all the children, then the parent prints a message than exits.

You may like to make the parent process a group leader first with a call to setpgrp , so that you can send a signal from any process in the group to all processes in the same group (the parent and its children) with kill(0, SIGHUP) . The parent process must install a signal handler for SIGHUP to be able to survive receiving SIGHUP or whatever other signal you may like to use for this purpose.