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我试图从同一个父进程创建多个进程,但它总是以超出预期的进程结束。我不知道怎么做,需要帮助。
我在网上找到一段代码并试过了,
int main ()
{
pid_t pid=0;
int i=0;
for (i=0; i<3; i++)
{
pid=fork();
switch(pid)
{
case 0:
{
cout<<"\nI am a child and my pid is:"<<getpid();
cout<<endl;
exit(0);
break;
}
default:
{
cout<<"\nI am a parent and my pid is: "<<getpid();
cout<<"\nMy child pid is: "<<pid;
cout<<endl;
wait(NULL);
break;
}
}
}
return 0;
}
此代码确实有效,并从同一父级创建3个子级。但是,这似乎是因为在创建每个子进程之后,它会立即终止。所以它不会在下一轮for循环中分叉更多的孙子进程。但我需要让这些子进程运行一段时间,并且它们需要与父母沟通。
最佳答案
子进程可能会立即中断循环以在外部继续其工作
int main ()
{
cout<<"\nI am a parent and my pid is: "<<getpid()<<endl;
pid_t pid;
int i;
for (i=0; i<3; i++)
{
pid=fork();
if(pid == -1)
{
cout<<"Error in fork()"<<endl;
return 1;
}
if(pid == 0)
break;
cout<<"My child "<<i<<" pid is: "<<pid<<endl;
}
if(pid == 0)
{
cout<<"I am a child "<<i<<" and my pid is "<<getpid()<<endl;
wait(NULL); // EDIT: this line is wrong!
}
else
{
cout<<"I am a parent :)"<<endl;
wait(NULL); // EDIT: this line is wrong!
}
return 0;
}
编辑
wait(NULL)
行错误。如果进程没有子进程处于活动状态,wait()
没有效果,因此在这里对子进程没有作用。父进程wait()
中的Otoh暂停执行,直到任何一个孩子退出。我们这里有三个孩子,所以得三次。另外,我们不能提前知道孩子们完成的顺序,所以我们需要更复杂的代码。像这样的:struct WORK_DESCRIPTION {
int childpid;
// any other data - what a child has to do
} work[3];
for(i=1; i<3; i++) {
pid=fork();
...
work[i].childpid = pid;
}
if(pid == 0) // in a child
{
do_something( work[i] );
}
else
{
int childpid;
while(childpid = wait(NULL), childpid != 0)
{
// a child terminated - find out which one it was
for(i=0; i<3; i++)
if(work[i].childpid == childpid)
{
// use the i-th child results here
}
}
// wait returned 0 - no more children to wait for
}
关于linux - 如何从同一个父节点派生多个进程?,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/27182511/