{"id":3486,"date":"2017-08-05T13:41:21","date_gmt":"2017-08-05T05:41:21","guid":{"rendered":"https:\/\/ixyzero.com\/blog\/?p=3486"},"modified":"2017-08-05T13:41:21","modified_gmt":"2017-08-05T05:41:21","slug":"linux%e4%b8%8b%e7%94%a8c%e8%af%ad%e8%a8%80%e9%80%9a%e8%bf%87hostname%e8%8e%b7%e5%8f%96%e5%af%b9%e5%ba%94ip","status":"publish","type":"post","link":"https:\/\/ixyzero.com\/blog\/archives\/3486.html","title":{"rendered":"Linux\u4e0b\u7528C\u8bed\u8a00\u901a\u8fc7HOSTNAME\u83b7\u53d6\u5bf9\u5e94IP"},"content":{"rendered":"

=Start=<\/p>\n

\u7f18\u7531\uff1a<\/h4>\n

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\u53c2\u8003\u89e3\u7b54\uff1a<\/h5>\n

\u96be\u9053\u662fstrncat\u7684bug\uff1f\u8fd8\u662f\u6545\u610f\u4e3a\u4e4b\uff1f<\/p>\n

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#include <stdio.h>\u00a0<\/code>\/\/printf<\/code><\/div>\n
#include <string.h>\u00a0<\/code>\/\/memset<\/code><\/div>\n
#include <stdlib.h>\u00a0<\/code>\/\/for exit(0);<\/code><\/div>\n
#include <sys\/socket.h><\/code><\/div>\n
#include <errno.h>\u00a0<\/code>\/\/For errno - the error number<\/code><\/div>\n
#include <netdb.h>\u00a0<\/code>\/\/hostent<\/code><\/div>\n
#include <arpa\/inet.h><\/code><\/div>\n
<\/div>\n
\/*<\/code><\/div>\n
Get ip from domain name (gethostbyname)<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0<\/code>int hostname_to_ip(char *\u00a0 , char *);<\/code><\/div>\n
\u00a0<\/code>*\/<\/code><\/div>\n
int<\/code>\u00a0hostname_to_ip(<\/code>char<\/code>\u00a0* hostname ,\u00a0<\/code>char<\/code>* ip)<\/code><\/div>\n
{<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0<\/code>struct hostent *he;<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0<\/code>struct in_addr **addr_list;<\/code><\/div>\n
<\/div>\n
\u00a0\u00a0\u00a0\u00a0<\/code>if<\/code>\u00a0( (he = gethostbyname( hostname ) ) == NULL) {<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/code>perror(<\/code>\"gethostbyname\"<\/code>);<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/code>return<\/code>\u00a01<\/code>;<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0<\/code>}<\/code><\/div>\n
<\/div>\n
\u00a0\u00a0\u00a0\u00a0<\/code>addr_list = (struct in_addr **) he->h_addr_list;<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0<\/code>int<\/code>\u00a0i;<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0<\/code>for<\/code>(i =\u00a0<\/code>0<\/code>; addr_list[i] != NULL; i++) {<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/code>printf(<\/code>\"strlen(ip)-1 = %d\\n\"<\/code>, strlen(ip)-<\/code>1<\/code>);<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/code>strncat(ip, inet_ntoa(*addr_list[i]), strlen(ip)-<\/code>1<\/code>);\u00a0<\/code>\/\/\u5728\u7b2c\u4e00\u4e2a\u5faa\u73af\u4e2dstrlen(ip)=0\uff0c\u6240\u4ee5strncat\u7684\u7b2c3\u4e2a\u53c2\u6570\u4e3a-1\uff0c\u6309\u7406\u6765\u8bf4\u5e94\u8be5\u51fa\u9519\u624d\u5bf9\uff0c\u4f46\u4e3a\u5565\u8fd8\u662f\u53ef\u4ee5\u6b63\u786e\u5b9e\u73b0\uff1f<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/code>if<\/code>(addr_list[i+<\/code>1<\/code>] != NULL)<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/code>strncat(ip,\u00a0<\/code>\",\"<\/code>,\u00a0<\/code>1<\/code>);<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/code>printf(<\/code>\"%s\\n\"<\/code>, inet_ntoa(*addr_list[i]));<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0<\/code>}<\/code><\/div>\n
<\/div>\n
\u00a0\u00a0\u00a0\u00a0<\/code>return<\/code>\u00a00<\/code>;<\/code><\/div>\n
}<\/code><\/div>\n
<\/div>\n
int<\/code>\u00a0main(<\/code>int<\/code>\u00a0argc ,\u00a0<\/code>char<\/code>\u00a0*argv[])<\/code><\/div>\n
{<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0<\/code>if<\/code>(argc <<\/code>2<\/code>) {<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/code>printf(<\/code>\"Please provide a hostname to resolve.\\n\"<\/code>);<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/code>exit(<\/code>1<\/code>);<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0<\/code>}<\/code><\/div>\n
<\/div>\n
\u00a0\u00a0\u00a0\u00a0<\/code>char<\/code>\u00a0*hostname = argv[<\/code>1<\/code>];<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0<\/code>char<\/code>\u00a0ip[<\/code>100<\/code>];<\/code><\/div>\n
\u00a0\u00a0\u00a0\u00a0<\/code>hostname_to_ip(hostname, ip);<\/code><\/div>\n
<\/div>\n
\u00a0\u00a0\u00a0\u00a0<\/code>printf(<\/code>\"\\n%s resolved to %s\\n\"<\/code>, hostname, ip);<\/code><\/div>\n
<\/div>\n
\u00a0\u00a0\u00a0\u00a0<\/code>return<\/code>\u00a00<\/code>;<\/code><\/div>\n
}<\/code><\/div>\n<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

&<\/p>\n

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# gcc hostname_to_ip.c -o hostname_to_ip<\/code><\/div>\n
# .\/hostname_to_ip www.baidu.com<\/code><\/div>\n
strlen(ip)-<\/code>1<\/code>\u00a0= -<\/code>1<\/code><\/div>\n
220.181<\/code>.<\/code>111.188<\/code><\/div>\n
strlen(ip)-<\/code>1<\/code>\u00a0=\u00a0<\/code>15<\/code><\/div>\n
220.181<\/code>.<\/code>112.244<\/code><\/div>\n
<\/div>\n
www.baidu.com resolved to\u00a0<\/code>220.181<\/code>.<\/code>111.188<\/code>,<\/code>220.181<\/code>.<\/code>112.244<\/code><\/div>\n<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
\u53c2\u8003\u94fe\u63a5\uff1a<\/h5>\n