进程间共享内存（信号量实现同步）
1 #include <stdio.h> 2 #include <stdlib.h> 3 #include <unistd.h> 4 #include <sys/types.h> 5 #include <sys/shm.h> 6 #include <sys/ipc.h> 7 #include <sys/sem.h> 8 #include <string.h> 9 int main(int argc, char* argv[]) 10 { 11 int running = 1; 12 int shid; 13 int semid; 14 int value; 15 int read_num; 16 FILE *stream; 17 char* sharem=NULL; 18 struct sembuf sem_b; 19 sem_b.sem_num = 0; 20 sem_b.sem_flg = SEM_UNDO; 21 22 if((semid = semget((key_t)123456,1,0666|IPC_CREAT))==-1) 23 { 24 perror("semget"); 25 exit(EXIT_FAILURE); 26 } 27 if(semctl(semid,0,SETVAL,0)==-1) 28 { 29 printf("sem init error"); 30 if(semctl(semid,0,IPC_RMID,0)!=0) 31 { 32 perror("semctl"); 33 exit(EXIT_FAILURE); 34 } 35 exit(EXIT_FAILURE); 36 } 37 shid = shmget((key_t)654321,(size_t)30,0600|IPC_CREAT); 38 if(shid == -1) 39 { 40 perror("shmget"); 41 exit(EXIT_FAILURE); 42 } 43 sharem = shmat(shid,NULL,0); 44 if(sharem==NULL) 45 { 46 perror("shmat"); 47 exit(EXIT_FAILURE); 48 } 49 stream = fopen("data.in","r"); 50 while(running) 51 { 52 // printf("write data operate\n"); 53 // while((semctl(semid,0,GETVAL))==1); 54 if((value=semctl(semid,0,GETVAL))==0) 55 { 56 57 // if((read_num = fread(sharem,20,1,stream))==0) 58 // running--; 59 if(fscanf(stream,"%s",sharem)!=EOF) 60 { 61 printf("%s\n",sharem); 62 sem_b.sem_op = 1; 63 if(semop(semid,&sem_b,1)==-1) 64 { 65 printf("error\n"); 66 exit(EXIT_FAILURE); 67 } 68 } 69 else break; 70 } 71 } 72 printf("send completed\n"); 73 fclose(stream); 74 shmdt(sharem); 75 return 0; 76 }
以上是sender进程。
1 /*receiver.c*/ 2 #include <stdio.h> 3 #include <stdlib.h> 4 #include <unistd.h> 5 #include <sys/types.h> 6 #include <sys/shm.h> 7 #include <sys/ipc.h> 8 #include <sys/sem.h> 9 #include <string.h> 10 int main(int argc, char *argv[]) 11 { 12 int running = 1; 13 char *shm_p = NULL; 14 int shmid; 15 int value; 16 int semid; 17 FILE *stream; 18 19 struct sembuf sem_b; 20 sem_b.sem_num=0; 21 sem_b.sem_flg=SEM_UNDO; 22 23 semid=semget((key_t)123456,1,0666|IPC_CREAT); 24 shmid = shmget((key_t)654321,(size_t)30,0600|IPC_CREAT); 25 shm_p = shmat(shmid,NULL,0); 26 printf("read data operate\n"); 27 //stream = fopen("data.out","w+"); 28 char buffer[50]; 29 while(running) 30 { 31 while((value=semctl(semid,0,GETVAL))==1) 32 { 33 stream = fopen("data.out","a+"); 34 sem_b.sem_op = -1; 35 if(semop(semid,&sem_b,1)==-1) 36 { 37 printf("error\n"); 38 exit(EXIT_FAILURE); 39 } 40 strcpy(buffer,shm_p); 41 printf("%s\n",buffer); 42 //fwrite(shm_p,20,1,stream); 43 fprintf(stream,"%s\n",buffer); 44 fclose(stream); 45 } 46 if(strcmp(shm_p,"end")==0) 47 running--; 48 } 49 shmdt(shm_p); 50 if(shmctl(shmid,IPC_RMID,0)!=0) 51 { 52 perror("shmctl"); 53 exit(EXIT_FAILURE); 54 } 55 if(semctl(semid,0,IPC_RMID,0)!=0) 56 { 57 perror("semctl"); 58 exit(EXIT_FAILURE); 59 } 60 return 0; 61 }
以上是receiver进程。
sender：从data.in中读取数据写入到共享内存。
receiver:从共享内存读数据，写入到data.out。
以end作为结束符。
用信号量作为同步机制。
