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  1. #include "sys/ipc.h"
  2. #include "sys/shm.h"
  3.  
  4. #include "unistd.h"
  5. #include "sys/types.h"
  6. #include "sys/wait.h"
  7.  
  8. #include "stdio.h"
  9. #include "stdlib.h"
  10.  
  11. int main(){
  12.     key_t key = 0x12345678;
  13.     int shmid = shmget(key, sizeof(int), IPC_CREAT | 0666);
  14.     if (fork() != 0){
  15.         int * ptr = (int *) shmat(shmid, 0, 0); 
  16.         printf("shmid parent = %d\n", shmid);
  17.         *ptr = 6;
  18.         shmdt(ptr);
  19.         wait(NULL);
  20.         shmctl(shmid, IPC_RMID, NULL);
  21.     }
  22.     else{
  23.         printf("shmid child = %d\n", shmid);
  24.         int * ptr = (int *) shmat(shmid, 0, 0); // Works as expected
  25.         printf("ptr address = %p\n", ptr);
  26.         shmdt(ptr);
  27.         printf("Now child can exit normally\n");
  28.     }
  29.     return 0;
  30. }
  31.  
Success #stdin #stdout 0.01s 5532KB
comments (?)
stdin
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Standard input is empty
stdout
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shmid child = 0
ptr address = 0x1552f8de6000
Now child can exit normally
shmid parent = 0
https://ideone.com/FQzNUA
language:
C (gcc 8.3)
created:
233 days ago
visibility:
secret

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