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#include <stdio.h>
#include <stdlib.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <time.h>
#include <unistd.h>
struct timespec ts = {
.tv_sec = 3468960000, // 2075-12-05 Destination timestamp
.tv_nsec = 0
};
void print_shmid_ds(struct shmid_ds *buf) {
printf("shm_perm.uid: %d \n", buf->shm_perm.uid);
printf("shm_perm.gid: %d \n", buf->shm_perm.gid);
printf("shm_perm.cuid: %d \n", buf->shm_perm.cuid);
printf("shm_perm.cgid: %d \n", buf->shm_perm.cgid);
printf("shm_perm.mode: %o \n", buf->shm_perm.mode);
printf("shm_segsz: %lu \n", buf->shm_segsz);
printf("shm_lpid: %d \n", buf->shm_lpid);
printf("shm_cpid: %d \n", buf->shm_cpid);
printf("shm_nattch: %lu \n", buf->shm_nattch);
printf("shm_atime: %s", buf->shm_atime ? ctime(&buf->shm_atime) : "Not set\n");
printf("shm_dtime: %s", buf->shm_dtime ? ctime(&buf->shm_dtime) : "Not set\n");
printf("shm_ctime: %s\n", ctime(&buf->shm_ctime));
}
int main() {
struct timespec ts_init, ts_final;
// Save system time
if (clock_gettime(CLOCK_REALTIME, &ts_init) == -1) {
perror("Error getting time");
return 1;
}
if (clock_settime(CLOCK_REALTIME, &ts) == -1) { // Set the time to after 2038
perror("Error setting time");
return 1;
}
key_t key = ftok(".", 'S');
int shmid = shmget(key, 1024, IPC_CREAT | 0666);
if (shmid == -1) {
perror("shmget");
exit(1);
}
struct shmid_ds buf;
if (shmctl(shmid, IPC_STAT, &buf) == -1) {
perror("shmctl");
exit(1);
}
printf("Shared Memory Segment Info:\n");
print_shmid_ds(&buf);
// Change to new permissions
buf.shm_perm.mode = 0600;
if (shmctl(shmid, IPC_SET, &buf) == -1) {
perror("shmctl IPC_SET failed");
shmctl(shmid, IPC_RMID, NULL);
exit(EXIT_FAILURE);
}
if ((buf.shm_ctime - ts.tv_sec > 60) || (ts.tv_sec - buf.shm_ctime > 60)) {
printf("\nShmctl get a error time! \n");
exit(EXIT_FAILURE);
}
printf("Shared Memory Segment Info:\n");
print_shmid_ds(&buf);
shmctl(shmid, IPC_RMID, NULL);
// Restore system time
clock_gettime(CLOCK_REALTIME, &ts_final);
ts_init.tv_sec = ts_init.tv_sec + ts_final.tv_sec - ts.tv_sec;
clock_settime(CLOCK_REALTIME, &ts_init);
return 0;
}
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