fig16.17

unix环境高级编程第二版配套源代码 unix环境高级编程第二版配套源代码

#include "apue.h"
#include <netdb.h>
#include <errno.h>
#include <syslog.h>
#include <sys/socket.h>

#define BUFLEN		128
#define MAXADDRLEN	256

#ifndef HOST_NAME_MAX
#define HOST_NAME_MAX 256
#endif

extern int initserver(int, struct sockaddr *, socklen_t, int);

void
serve(int sockfd)
{
	int			n;
	socklen_t	alen;
	FILE		*fp;
	char		buf[BUFLEN];
	char		abuf[MAXADDRLEN];

	for (;;) {
		alen = MAXADDRLEN;
		if ((n = recvfrom(sockfd, buf, BUFLEN, 0,
		  (struct sockaddr *)abuf, &alen)) < 0) {
			syslog(LOG_ERR, "ruptimed: recvfrom error: %s",
			  strerror(errno));
			exit(1);
		}
		if ((fp = popen("/usr/bin/uptime", "r")) == NULL) {
			sprintf(buf, "error: %s\n", strerror(errno));
			sendto(sockfd, buf, strlen(buf), 0,
			  (struct sockaddr *)abuf, alen);
		} else {
			if (fgets(buf, BUFLEN, fp) != NULL)
				sendto(sockfd, buf, strlen(buf), 0,
				  (struct sockaddr *)abuf, alen);
			pclose(fp);
		}
	}
}

int
main(int argc, char *argv[])
{
	struct addrinfo	*ailist, *aip;
	struct addrinfo	hint;
	int				sockfd, err, n;
	char			*host;

	if (argc != 1)
		err_quit("usage: ruptimed");
#ifdef _SC_HOST_NAME_MAX
	n = sysconf(_SC_HOST_NAME_MAX);
	if (n < 0)	/* best guess */
#endif
		n = HOST_NAME_MAX;
	host = malloc(n);
	if (host == NULL)
		err_sys("malloc error");
	if (gethostname(host, n) < 0)
		err_sys("gethostname error");
	daemonize("ruptimed");
	hint.ai_flags = AI_CANONNAME;
	hint.ai_family = 0;
	hint.ai_socktype = SOCK_DGRAM;
	hint.ai_protocol = 0;
	hint.ai_addrlen = 0;
	hint.ai_canonname = NULL;
	hint.ai_addr = NULL;
	hint.ai_next = NULL;
	if ((err = getaddrinfo(host, "ruptime", &hint, &ailist)) != 0) {
		syslog(LOG_ERR, "ruptimed: getaddrinfo error: %s",
		  gai_strerror(err));
		exit(1);
	}
	for (aip = ailist; aip != NULL; aip = aip->ai_next) {
		if ((sockfd = initserver(SOCK_DGRAM, aip->ai_addr,
		  aip->ai_addrlen, 0)) >= 0) {
			serve(sockfd);
			exit(0);
		}
	}
	exit(1);
}