linux c 共享内存读写操作

nclude <unistd.h> #include <stdlib.h> #include <stdio.h> #include <sys/shm.h> #include <sys/time.h> #include <time.h> #include "ShareData.h" int main() { int running = 1;//程序是否继续运行的标志 void *shm = NULL;//分配的共享内存的原始首地址 struct shared_use_t *shared;//指向shm int shmid;//共享内存标识符 //创建共享内存 shmid = shmget((key_t)123456, sizeof(struct shared_use_t)*52400000, 0666|IPC_CREAT); if(shmid == -1) { fprintf(stderr, "shmget failed\n"); exit(EXIT_FAILURE); } //将共享内存连接到当前进程的地址空间 shm = shmat(shmid, 0, 0); if(shm == (void*)-1) { fprintf(stderr, "shmat failed\n"); exit(EXIT_FAILURE); } printf("\nMemory attached at %X\n", (int)shm); //设置共享内存 shared = (struct shared_use_t*)shm; //shared->written = 0; float time_use=0; struct timeval start; struct timeval end; gettimeofday(&start,NULL); while(running)//读取共享内存中的数据 { //printf("You wrote: %s", shared->text); //sleep(rand() % 3); //读取完数据，设置written使共享内存段可写 shared->written = 0; //输入了end，退出循环（程序） if(strncmp(shared->text, "end", 3) == 0) { running = 0; break; } shared = shared + 1; while(1) { if(shared == NULL) { sleep(2); } else { break; } } } gettimeofday(&end,NULL); time_use=(end.tv_sec-start.tv_sec)*1000000+(end.tv_usec-start.tv_usec);//微秒 printf("time_use is %f\n",time_use); //把共享内存从当前进程中分离 if(shmdt(shm) == -1) { fprintf(stderr, "shmdt failed\n"); exit(EXIT_FAILURE); } //删除共享内存 if(shmctl(shmid, IPC_RMID, 0) == -1) { fprintf(stderr, "shmctl(IPC_RMID) failed\n"); exit(EXIT_FAILURE); } exit(EXIT_SUCCESS); }