是否可以恢复被杀死的子进程？

Question

我正在尝试为基本流程控制块编写程序，下面的代码显示了我在测试阶段所做的事情，我想知道我们是否可以恢复一个孩子一旦被杀死而不是再次分叉一个新孩子是的，我们该怎么做。 提前致谢！
代码：
`

    #include<sys/types.h> 
    #include<sys/wait.h>
    #include<unistd.h>
    #include<time.h>
    #include<stdio.h>
    #include<unistd.h>
    #include<time.h>
    #include<stdio.h>
    #include<stdlib.h>
int hell()
    {  
   int j;
   for(j=1;j<6;j++)
   printf("%d hello\n",j);` 
    }  
int hello(k)
    {    
int i
for(i=1;i<15;i++
printf("%5d hello \n", i);

    }  
void sigint()
    {  
    signal(SIGCONT,sigint); /* reset signal */
    printf("CHILD: I have received a SIGINT\n"); 
    }  
int main()
    {
 int i, status;
 pid_t childID, endID,end1id,parentid;
 time_t when;

label: if ((childID = fork()) == -1) {
    perror("fork error");
    exit(EXIT_FAILURE);
 }
else if (childID == 0) {
    time(&when);hell();
    printf("k value %d\n",hello(5));
    printf("Child process started at %s\n", ctime(&when));
    printf("child PID : %d \n",getpid());

    hello();
    sleep(10);
    //kill(childID, SIGKILL);                 

    exit(EXIT_SUCCESS);
 }
 }
else {
    time(&when);
    printf("Parent process started at %s", ctime(&when));
    printf("parent PID : %d\n",getpid());
            hell();
       parentid = getpid();
for(i = 0; i < 15; i++) {
       endID =waitpid(childID,&status,WNOHANG|WUNTRACED);     
    printf("endid: %d\n",endID);
       end1id = waitpid(parentid, &status, WNOHANG|WUNTRACED);    
       if (endID == -1) {  
          perror("waitpid error");
          exit(EXIT_FAILURE);
       }
       else if (endID == 0) {
          time(&when);
          printf("Parent waiting for child at %s", ctime(&when));
          sleep(1);
       }  
       else if (endID == childID) {

          if (WIFEXITED(status))
             printf("Child ended normally\n\n");
          else if (WIFSIGNALED(status)){
        printf("Child ended because of an uncaught signal\n");goto label;}
          else if (WIFSTOPPED(status)){
          printf("Child process has stopped\n");goto label;}
          exit(EXIT_SUCCESS);
       }  
}  
}  

Answer 1

当您向子进程发出 kill 命令时，您可以使用 SIGSTOP 将其挂起而不使其死亡，然后使用 SIGCONT 将其从中断处恢复。

#include <stdio.h>
#include <unistd.h>
#include <signal.h>

int main() {
   pid_t childId;

   if ( ( childId = fork() ) == -1 ) {
      printf( "child fork failed\n" );

   } else if ( childId == 0 ) {
      int i = 0;
      while ( 1 ) {
         printf( "infinite child loop ==> %d\n", ++i );
         sleep( 1 );
      }

   } else {
      printf( "parent: child started OK\n" );
      sleep( 5 );
      printf( "parent: stopping child - but letting it live\n" );
      kill( childId, SIGSTOP );
      sleep( 5 );
      printf( "parent: resuming child since it stopped but never really died\n" );
      kill( childId, SIGCONT );
      printf( "parent: child should be running again where it left off\n" );
      sleep( 5 );

   }
}

输出：

parent: child started OK
infinite child loop ==> 1
infinite child loop ==> 2
infinite child loop ==> 3
infinite child loop ==> 4
infinite child loop ==> 5
infinite child loop ==> 6
parent: stopping child - but letting it live
parent: resuming child since it stopped but never really died
parent: child should be running again where it left off
infinite child loop ==> 7
infinite child loop ==> 8
infinite child loop ==> 9
infinite child loop ==> 10
infinite child loop ==> 11
infinite child loop ==> 12