example26.c

LinuxNetProgramming Linux网络编程基础实例

#include	<sys/msg.h>
#include	<sys/ipc.h>
#include	<stdio.h>

#define MAXMESGDATA     1000
#define SVMSG_MODE      777

struct mymesg {
        long        mesg_len;       /* #bytes in mesg_data, can be 0 */
        long        mesg_type;      /* message type, must be > 0 */
        char        mesg_data[MAXMESGDATA];
};

	
size_t
msg_send(int id, struct mymesg *mptr)
{
	        return(msgsnd(id, &(mptr->mesg_type), mptr->mesg_len, 0));
}
/* end mesg_send */
size_t
mesg_recv(int id, struct mymesg *mptr)
{
	        ssize_t n;

		n = msgrcv(id, &(mptr->mesg_type), MAXMESGDATA, mptr->mesg_type, 0);
		mptr->mesg_len = n;             /* return #bytes of data */
		
		return(n);                              /* -1 on error, 0 at EOF, else >0 */
}

int
main()
{
	int		msgid;
	size_t		len;
	ssize_t 	n;
	char		*ptr;
	struct mymesg	mesg;

	msgid = msgget(4321, 0);	/* 打开消息队列 */
	snprintf(mesg.mesg_data, MAXMESGDATA, "%ld", (long)getpid());
	len = strlen(mesg.mesg_data);
	ptr = mesg.mesg_data + len;
	fgets(ptr, MAXMESGDATA - len, stdin); /* 读入路径名 */
	len = strlen(mesg.mesg_data);
	if (mesg.mesg_data[len-1] == '\n')
		len--;
	mesg.mesg_len = len;
	mesg.mesg_type = 1;
	msg_send(msgid, &mesg);				/* 将路径名写入消息队列 */
	mesg.mesg_type = getpid();			/* 以自己的进程号做为消息类型 */
	while((n = mesg_recv(msgid, &mesg)) > 0)		/* 从消息队列中读回服务进程返回的消息*/
		write(stdout, mesg.mesg_data);	/* 将获得的文件内容写到标准输出 */
	exit(0);
}