Linux ipc------ 信号量+共享内存编程

来源：互联网发布：龙岩淘宝诈骗编辑：程序博客网时间：2024/05/21 09:47

此程序实现没有亲缘关系的两个进程间通过共享内存进行数据通信。

同时，使用信号量保证两个进程的读写同步：发送方在写共享内存时，接收方不能读数据；接收方在读数据时，发送方不能写数据。

1、fork创建子进程

2、使用二元信号量，同步读写端

fork_shm.c

#include<stdio.h>#include<sys/types.h>#include<unistd.h>#include"send_recv.h"int main(void){printf("fork test!\n");pid_t pid;if((pid=fork())==-1)printf("fork error");else if(pid==0){printf("in the child process\n");printf("the father process's ppid is %d\n",getppid());fork_recv();}else{//sleep(1);printf("in the parent process\n");printf("the son process's pid is %d\n",getpid());fork_send();}return 0;}

send_recv.c

#include"fork_recv.c"#include"fork_send.c"int fork_recv();int fork_send();

fork_send.c

#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <sys/types.h>#include <sys/shm.h>#include <sys/ipc.h>#include <sys/sem.h>#include <string.h>int fork_send(){int running=1;int shid;int semid;int value;void *sharem=NULL;struct sembuf  sem_b;sem_b.sem_num = 0;sem_b.sem_flg = SEM_UNDO;if((semid=semget((key_t)123456,1,0666|IPC_CREAT))==-1){perror("semget");exit(EXIT_FAILURE);}if (semctl(semid, 0, SETVAL, 0) == -1){printf("sem init error");        if(semctl(semid,0,IPC_RMID,0)!=0){perror("semctl");exit(EXIT_FAILURE);}exit(EXIT_FAILURE);}shid=shmget((key_t)654321,(size_t)2048,0600|IPC_CREAT);if(shid==-1){perror("shmget");exit(EXIT_FAILURE);}sharem=shmat(shid,NULL,0);if(sharem==NULL){perror("shmat");exit(EXIT_FAILURE);}while(running){if((value=semctl( semid, 0, GETVAL ))==0){printf("write data operate\n");printf("please input something:\n");scanf("%s",sharem);sem_b.sem_op = 1;if (semop(semid, &sem_b, 1) == -1) {fprintf(stderr, "semaphore_p failed\n");exit(EXIT_FAILURE);}}if(strcmp(sharem,"end")==0)running--;}shmdt(sharem);return 0;}

fork_recv.c

#include <stdio.h>#include <stdlib.h>#include <sys/types.h>#include <unistd.h>#include <string.h>#include <sys/ipc.h>#include <sys/shm.h>#include <sys/sem.h>int fork_recv(){int running=1;char *shm_p=NULL;int shmid;int semid;int value;struct sembuf  sem_b;sem_b.sem_num = 0;sem_b.sem_flg = SEM_UNDO;if((semid=semget((key_t)123456,1,0666|IPC_CREAT))==-1){perror("semget");exit(EXIT_FAILURE);}shmid=shmget((key_t)654321,(size_t)2048,0600|IPC_CREAT);if(shmid==-1){perror("shmget");exit(EXIT_FAILURE);}shm_p=shmat(shmid,NULL,0);if(shm_p==NULL){perror("shmat");exit(EXIT_FAILURE);}while(running){if((value=semctl( semid, 0, GETVAL ))==1){printf("read data operate\n");sem_b.sem_op = -1;if (semop(semid, &sem_b, 1) == -1) {fprintf(stderr, "semaphore_p failed\n");exit(EXIT_FAILURE);}printf("%s\n",shm_p);}if(strcmp(shm_p,"end")==0)running--;}shmdt(shm_p);if(shmctl(shmid,IPC_RMID,0)!=0){perror("shmctl");exit(EXIT_FAILURE);}if(semctl(semid,0,IPC_RMID,0)!=0){perror("semctl");exit(EXIT_FAILURE);}return 0;}

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