程序主要參考：http://hector.blog.51cto.com/4229131/758930

#include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <sys/ipc.h> #include <sys/sem.h> #include <sys/stat.h> #include <fcntl.h> union semun //必須自己定義 { int val; struct semid_ds *buf; unsigned short int *array; struct seminfo *__buf; }; void p(int k) {sb.sem_num = k; //將k號信號量sb.sem_op = -1; //減1sb.sem_flg = SEM_UNDO; semop(semid, &sb, 1); //原子p操作，//semop(int semid,struct sembuf semoparray[],size_t nops)對信號量集合semid進行p操作，操作的內容在semoparray,nops表明前面數組的大小 }void v(int k) {sb.sem_num = k; //將k號信號量sb.sem_op = 1; //加1sb.sem_flg = SEM_UNDO; semop(semid, &sb, 1); //操作信號量 }int main(void) { char* buf_child[]={"this", "is", "the", "child", "process"}; char* buf_father[]={"father", "say", "hello", "to", "child"}; int i = 0, semid, fd; pid_t pid; struct sembuf sb; //信號量操作union semun sem; semid = semget(1000, 2, 0666 | IPC_CREAT); //申請信號量組，包含2個信號量sem.val = 0; //semctl(int semid,int semnum,int cmd,union semun)對信號量集合中的第semnum號信號進行cmd操作，操作的具體數值放在semun中semctl(semid, 0, SETVAL, sem); //初始化0號信號量為0sem.val = 1; semctl(semid, 1, SETVAL, sem); //初始化1號信號量為1fd=open("tmp",O_CREAT|O_TRUNC|O_WRONLY,0666); pid = fork(); switch (pid) { case -1: perror("fork fail"); break; case 0: /* child consume */ srand((unsigned int)getpid()); while (i < 5) { p(1);//child 只看1號信號量write(fd,buf_child[i], strlen(buf_child[i])); sleep(rand()); write(fd,&" ", 1); i++; v(0);} break; default:/* parent production */ srand((unsigned int)getpid()); while (i < 5) { p(0);//parent 只看0號信號量write(fd,buf_father[i], strlen(buf_father[i])); sleep(rand()); write(fd,&" ", 1); i++; v(1);} break; } return 0; }

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