ruptimed-fd.c

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 <fcntl.h>
#include <sys/socket.h>
#include <sys/wait.h>

#define QLEN 10

#ifndef HOST_NAME_MAX
#define HOST_NAME_MAX 256
#endif

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

void
serve(int sockfd)
{
	int		clfd, status;
	pid_t	pid;

	for (;;) {
		clfd = accept(sockfd, NULL, NULL);
		if (clfd < 0) {
			syslog(LOG_ERR, "ruptimed: accept error: %s",
			  strerror(errno));
			exit(1);
		}
		if ((pid = fork()) < 0) {
			syslog(LOG_ERR, "ruptimed: fork error: %s",
			  strerror(errno));
			exit(1);
		} else if (pid == 0) {	/* child */
			/*
			 * The parent called daemonize ({Prog daemoninit}), so
			 * STDIN_FILENO, STDOUT_FILENO, and STDERR_FILENO
			 * are already open to /dev/null.  Thus, the call to
			 * close doesn't need to be protected by checks that
			 * clfd isn't already equal to one of these values.
			 */
			if (dup2(clfd, STDOUT_FILENO) != STDOUT_FILENO ||
			  dup2(clfd, STDERR_FILENO) != STDERR_FILENO) {
				syslog(LOG_ERR, "ruptimed: unexpected error");
				exit(1);
			}
			close(clfd);
			execl("/usr/bin/uptime", "uptime", (char *)0);
			syslog(LOG_ERR, "ruptimed: unexpected return from exec: %s",
			  strerror(errno));
		} else {		/* parent */
			close(clfd);
			waitpid(pid, &status, 0);
		}
	}
}

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_STREAM;
	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_STREAM, aip->ai_addr,
		  aip->ai_addrlen, QLEN)) >= 0) {
			serve(sockfd);
			exit(0);
		}
	}
	exit(1);
}