cal*_*kon 6 c fork pid process
我的问题是:
1.)如何让父进程永远死？我知道这没有完成,因为父亲是第一个运行的pid,但我不知道如何改变它.
2.)如何让我的子进程像他一样同时执行？我甚至把这个数字提高到很高,看它是不是巧合,但似乎不是.
编辑:解决方案
1.)在内部默认
2中添加了两次wait(NULL).)正在发生.用睡眠(1)来证明它.
我的代码如下
#include <stdio.h>
int main() {
int pid, i;
pid = fork();
switch(pid) {
case -1:
// error
printf("Fork error");
break;
case 0:
// child process
printf("First child is born, my pid is %d\n", getpid());
for(i=1; i<10; i++)
printf("First child executes iteration %d\n", i);
printf("First child dies quietly.\n");
break;
default:
// parent process
printf("Parent process is born, my pid is %d\n", getpid());
pid = fork();
switch(pid) {
case -1:
// error
printf("Fork error");
break;
case 0:
// child process
printf("Second child is born, my pid is %d\n", getpid());
for(i=1; i<10; i++)
printf("Second child executes iteration %d\n", i);
printf("Second child dies quietly.\n");
break;
default:
// parent process
printf("Parent process dies quietly.");
}
}
return 0;
}
我的输出总是如下所示:
Parent process is born, my pid is 7847 First child is born, my pid is 7848 First child executes iteration: 1 First child executes iteration: 2 First child executes iteration: 3 First child executes iteration: 4 First child executes iteration: 5 First child executes iteration: 6 First child executes iteration: 7 First child executes iteration: 8 First child executes iteration: 9 First child executes iteration: 10 First child dies quietly. Parent process dies quietly. Second child is born, my pid is 7849 Second child executes iteration 1 Second child executes iteration 2 Second child executes iteration 3 Second child executes iteration 4 Second child executes iteration 5 Second child executes iteration 6 Second child executes iteration 7 Second child executes iteration 8 Second child executes iteration 9 Second child executes iteration 10 Second child dies quietly.
我的任务是:
编写一个C程序("procs.c"),它创建三个进程:一个创建两个子进程的父进程.
第一个孩子应该做以下事情:
显示"第一个孩子出生,我的pid是......"
显示十次"第一个子进行迭代X"的消息,其中X是迭代次数
显示"第一个孩子安静地死去."
第二个孩子应该做以下事情:
显示"第二个孩子出生,我的pid是......"
显示十次消息"第二个子进行迭代X",其中X是迭代次数
显示"第二个孩子悄然死去".
父进程应执行以下操作:
显示"父进程诞生,我的pid是......"
创造第一个孩子
创造第二个孩子
显示"父进程悄然死亡".
使用gcc编译程序并命名可执行文件"procs".多次执行程序并注意两个孩子的输出如何交织.
该程序的可能输出是:
nova> ./procs Parent process is born, my pid is 7847 First child is born, my pid is 7848 First child executes iteration: 1 First child executes iteration: 2 First child executes iteration: 3 First child executes iteration: 4 First child executes iteration: 5 Second child is born, my pid is 7849 Second child executes iteration 1 Second child executes iteration 2 Second child executes iteration 3 First child executes iteration: 6 Second child executes iteration 4 Second child executes iteration 5 Second child executes iteration 6 First child executes iteration: 7 Second child executes iteration 7 Second child executes iteration 8 Second child executes iteration 9 Second child executes iteration 10 Second child dies quietly. First child executes iteration: 8 First child executes iteration: 9 First child executes iteration: 10 First child dies quietly. Parent process dies quietly.
适当的父进程应该等待（使用wait()或waitpid()或特定于平台的变体）其子进程在退出之前死亡。
并发执行需要调度程序获得运行的机会。您可以通过适当的睡眠（微睡眠、纳米睡眠）操作来强制解决该问题。一些系统调用会有所帮助（所以fflush(0)可能会有所帮助）。
#include <stdio.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>
int main(void)
{
int pid, i;
struct timespec tw = { .tv_sec = 0, .tv_nsec = 10000000 };
pid = fork();
switch(pid)
{
case -1:
printf("Fork error");
break;
case 0:
printf("First child is born, my pid is %d\n", getpid());
for(i=1; i<10; i++)
{
printf("First child executes iteration %d\n", i);
nanosleep(&tw, 0);
}
printf("First child dies quietly.\n");
break;
default:
printf("Parent process is born, my pid is %d\n", getpid());
pid = fork();
switch(pid)
{
case -1:
printf("Fork error");
break;
case 0:
printf("Second child is born, my pid is %d\n", getpid());
for(i=1; i<10; i++)
{
printf("Second child executes iteration %d\n", i);
nanosleep(&tw, 0);
}
printf("Second child dies quietly.\n");
break;
default:
printf("Parent process waiting for children.\n");
int corpse;
int status;
while ((corpse = waitpid(0, &status, 0)) > 0)
printf("Child %d died with exit status 0x%.4X\n", corpse, status);
printf("Parent process dies quietly.\n");
break;
}
}
return 0;
}
输出示例：
Parent process is born, my pid is 46624
First child is born, my pid is 46625
First child executes iteration 1
Parent process waiting for children.
Second child is born, my pid is 46626
Second child executes iteration 1
First child executes iteration 2
Second child executes iteration 2
First child executes iteration 3
Second child executes iteration 3
First child executes iteration 4
Second child executes iteration 4
Second child executes iteration 5
First child executes iteration 5
Second child executes iteration 6
First child executes iteration 6
Second child executes iteration 7
First child executes iteration 7
Second child executes iteration 8
First child executes iteration 8
Second child executes iteration 9
First child executes iteration 9
First child dies quietly.
Second child dies quietly.
Child 46625 died with exit status 0x0000
Child 46626 died with exit status 0x0000
Parent process dies quietly.
请注意，10 毫秒的延迟几乎强制交替执行。如果没有类似的东西，你就会被系统及其调度程序的特性所困扰，而且许多现代机器都太快了！