reader.c

此源码是著名的教材BeginningLinux Programming中文名字叫Linux程序设计书中的源代码

#include "sharemem.h"

int main()
{
	int	semid, shmid;
	char	*shmaddr;
	
	if ((shmid = createshm(".", 'm', SHM_SIZE)) == -1)
	{
		exit (1);
	}
	
	if((shmaddr = shmat (shmid, (char *)0, 0)) == (char *)-1)
	{
		perror ("attach shared memory error!\n");
		exit (1);
	}
	
	if((semid = opensem("." ,'s')) == -1)
	{
		exit (1);
	}
	
	while(1)
	{
		printf("reader: ");
		wait_sem(semid,0);		/* 等待信号值为1 */
		sem_p(semid,0);			/* P操作 */
		
		printf("%s\n", shmaddr);
		sleep(10);			/* 使writer处于阻塞状态 */
		
		sem_v(semid,0);			/* V操作 */
		sleep(10);			/* 等待writer进行写操作 */
	}
}