ipcs    -m    查看当前共享内存
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
步骤:1. ftok2. shmget3. shmat4．进程间通信fork5. shmdt6. shmct1

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include csys/shm.h>int main(int argc,const char *arg[]{key_t key = ftok( "/",1);if (key --1){perror("ftok");return -1;}int shmid = shmget(key,1024，IPC_CREAT|0666);if(shmid == -1){perror("shmget");goto XXX;}printf("shmid: %d\n",shmid);system("ipcs -m");char *p = shmat(shmid,NULL,0);if(p == NULL){perror("shmat");goto XXX;}//forkpid_tpid = fork( );if(pid <0){perror("fork");goto XXX;}else if(pid == 0){//子进程写操作char buf[64]= {0};while(1){gets(buf);strcpy(p, buf);if(strncmp( buf, "quit",4) == 0){break;}}
}
else{
//父进程读操作waitpid (-1,NULL,WNOHANG);while(1){printf("p=%s\n",p);sleep(1);if(strncmp(p,"quit",4) == 0){break;}}}int ret = shmdt(p);if(ret == 1){perror("shmdt");goto XXX;}ret = shmctl(shmid,IPC_RMID,NULL);if(ret == -1){perror("shmctl");goto XXX;}
XXX:sleep(2);char str[100] = {0};sprintf(str,"ipcrm -m%d",shmid);system(str);system("ipcs -m");return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/sem.h>union semun {int val;  /* Value for SETVAL */struct semid_ds *buf;  unsigned short  *array;struct seminfo  *__buf;
};/*
struct sembuf{unsigned short sem_num;short sem_op;short sem_flg;
};
*/int main(int argc, const char *argv[])
{key_t key = ftok("/", 1);if(key == -1){perror("ftok");return -1;}int shmid = shmget(key, 1024, IPC_CREAT|0666);if(shmid == -1){perror("shmget");goto xxx;}printf("shmid:%d\n",shmid);system("ipcs -m");char *p = shmat(shmid, NULL, 0);if(p == NULL){perror("shmat");goto xxx;}//加入信号灯集来控制共享内存int semid = semget(key, 2, IPC_CREAT|0666);if(semid == -1){perror("semget");goto xxx;}//设置初值union semun sem0 = {0};union semun sem1 = {1};//设置编号semctl(semid, 0, SETVAL, sem0);semctl(semid, 1, SETVAL, sem1);//fork创建新进程pid_t pid = fork();if(pid < 0){perror("fork");goto xxx;}else if(pid == 0){//子进程 写操作char buf[64] = {0};struct sembuf sem0; //定义一个信号灯sem0sem0.sem_num = 1; //编号sem0.sem_op = -1; //PV操作 +1 -1sem0.sem_flg = 0;struct sembuf sem1;sem1.sem_num = 0;sem1.sem_op = 1;sem1.sem_flg = 0;while(1){semop(semid, &sem0, 1);gets(buf);strcpy(p, buf);if(strncmp(buf, "quit", 4) == 0){break;}semop(semid, &sem1, 1);}}else{//父进程 读操作waitpid(-1, NULL, WNOHANG);struct sembuf sem0;sem0.sem_num = 0;sem0.sem_op = -1;sem0.sem_flg = 0;struct sembuf sem1;sem1.sem_num = 1;sem1.sem_op = 1;sem1.sem_flg = 0;while(1){semop(semid, &sem0, 1);printf("p=%s\n", p);sleep(1);if(strncmp(p, "quit", 4) == 0){break;}semop(semid, &sem1, 1);}}int ret = semctl(semid, 0|1, IPC_RMID);if(ret == -1){perror("semctl");goto xxx;}ret = shmdt(p);if(ret == -1){perror("shmdt");goto xxx;}ret = shmctl(shmid, IPC_RMID, NULL);if(ret == -1){perror("shmctl");goto xxx;}xxx:    sleep(2); //防止出错char str[100] = {0};sprintf(str, "ipcrm -m %d", shmid);system(str);system("ipcs -m");return 0;
}