进程间通信之信号量--使用信号实现生产者消费者问题
生产者消费者是数学中的一个经典的问题，也是编程中的一个经典问题。
本示例采用信号量来解决这个问题，其实，最终也就是进程之间同步的问题。
生产者源代码如下：
#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <sys/ipc.h>#include <sys/stat.h>#include <sys/sem.h>int sem_id;void init(){key_t key;int ret;unsigned short sem_array[2]; //0代表生产者，1代表消费者union semun{int val;struct semid_ds *buf;unsigned short *array;}arg;key=ftok(".",'s');sem_id=semget(key,2,0777|IPC_CREAT);sem_array[0]=0;sem_array[1]=100;arg.array=sem_array;ret=semctl(sem_id,0,SETALL,arg);if(ret==-1){perror("semctl");exit(1);}printf("productor init is %d\n",semctl(sem_id,0,GETVAL));printf("consumer init is %d\n",semctl(sem_id,1,GETVAL));}void del(){semctl(sem_id,IPC_RMID,0);}int main(){struct sembuf sops[2];int retv;sops[0].sem_num= 0;sops[0].sem_op = 1;sops[0].sem_flg = 0;sops[1].sem_num= 1;sops[1].sem_op = -1;sops[1].sem_flg = 0;init();printf("this is productor\n");while(1){printf("\n\nbefore produce\n");printf("productor number is %d\n",semctl(sem_id,0,GETVAL));printf("space number is %d\n",semctl(sem_id,1,GETVAL));retv=semop(sem_id,&sops[1],1);//if(retv==-1)printf("no work semo on sops[0] retv%d\n",retv);printf("now producting....\n");retv=semop(sem_id,&sops[0],1);//if(retv==-1)printf("no work semo on sops[0] retv=%d\n",retv);printf("\nafter produce\n");printf("productor number is %d\n",semctl(sem_id,0,GETVAL));printf("space number is %d\n",semctl(sem_id,1,GETVAL));sleep(1);}del();return 0;}
消费者源代码如下：
#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <sys/ipc.h>#include <sys/stat.h>#include <sys/sem.h>int sem_id;void init(){key_t key;key=ftok(".",'s');sem_id=semget(key,2,0777|IPC_CREAT);}int main(){struct sembuf sops[2];sops[0].sem_num= 0;sops[0].sem_op = -1;sops[0].sem_flg = 0;sops[1].sem_num= 1;sops[1].sem_op = 1;sops[1].sem_flg = 0;init();printf("this is customer\n");while(1){printf("\n\nbefore consumer\n");printf("productor number is %d\n",semctl(sem_id,0,GETVAL));printf("space number is %d\n",semctl(sem_id,1,GETVAL));semop(sem_id,&sops[0],1);printf("now consuming....\n");semop(sem_id,&sops[1],1);printf("\nafter consume\n");printf("productor number is %d\n",semctl(sem_id,0,GETVAL));printf("space number is %d\n",semctl(sem_id,1,GETVAL));sleep(3);}return 0;}