C源码:通过IP地址查找主机名 findip.c

文章类别：C语言程序设计 | 发表日期:2008-9-24 14:38:01

/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
*
* Filename: findip.c
* Created : Nov. 10th 1995 @ 4:30pm
* Author : SrfRoG (srfrog@itek.net)
* Descrip.: This cute little program will attempt to resolve
* an IP address to its hostname. Then prints the results
* to standard output.
* ---------------------------------------------------------------------
* To compile this program:
* Linux: gcc -O2 -m486 -s -o findip findip.c
* AIX, BSD: gcc -O2 -s -o findip findip.c
* SunOS: gcc -O2 -lnsl -s -o findip findip.c
* Other: cc -o findip findip.c
*/

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

int main(argc, argv)
int argc;
char **argv;
{
struct hostent *ip;
unsigned long hostname;

if (argc != 2)
{
printf("Need to specify an IP address.\n");
exit(1);
}
if ((hostname = inet_addr(argv[1])) == -1)
{
printf("Could not find %s\n", argv[1]);
exit(1);
}
if ((ip = gethostbyaddr((char *)&hostname, sizeof(long), AF_INET)) != NULL)
printf("%s is %s\n", argv[1], ip->h_name);
else
printf("Could not resolve %s\n", argv[1]);
return 0;
}

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