210 lines
6.1 KiB
C
210 lines
6.1 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* Mini nslookup implementation for busybox
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*
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* Copyright (C) 1999,2000 by Lineo, inc. and John Beppu
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* Copyright (C) 1999,2000,2001 by John Beppu <beppu@codepoet.org>
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*
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* Correct default name server display and explicit name server option
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* added by Ben Zeckel <bzeckel@hmc.edu> June 2001
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*
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* Licensed under GPLv2 or later, see file LICENSE in this source tree.
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*/
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//config:config NSLOOKUP
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//config: bool "nslookup (4.5 kb)"
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//config: default y
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//config: help
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//config: nslookup is a tool to query Internet name servers.
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//applet:IF_NSLOOKUP(APPLET(nslookup, BB_DIR_USR_BIN, BB_SUID_DROP))
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//kbuild:lib-$(CONFIG_NSLOOKUP) += nslookup.o
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//usage:#define nslookup_trivial_usage
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//usage: "[HOST] [SERVER]"
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//usage:#define nslookup_full_usage "\n\n"
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//usage: "Query the nameserver for the IP address of the given HOST\n"
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//usage: "optionally using a specified DNS server"
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//usage:
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//usage:#define nslookup_example_usage
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//usage: "$ nslookup localhost\n"
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//usage: "Server: default\n"
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//usage: "Address: default\n"
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//usage: "\n"
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//usage: "Name: debian\n"
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//usage: "Address: 127.0.0.1\n"
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#include <resolv.h>
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#include "libbb.h"
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/*
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* I'm only implementing non-interactive mode;
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* I totally forgot nslookup even had an interactive mode.
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*
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* This applet is the only user of res_init(). Without it,
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* you may avoid pulling in _res global from libc.
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*/
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/* Examples of 'standard' nslookup output
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* $ nslookup yahoo.com
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* Server: 128.193.0.10
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* Address: 128.193.0.10#53
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*
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* Non-authoritative answer:
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* Name: yahoo.com
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* Address: 216.109.112.135
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* Name: yahoo.com
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* Address: 66.94.234.13
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*
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* $ nslookup 204.152.191.37
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* Server: 128.193.4.20
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* Address: 128.193.4.20#53
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*
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* Non-authoritative answer:
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* 37.191.152.204.in-addr.arpa canonical name = 37.32-27.191.152.204.in-addr.arpa.
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* 37.32-27.191.152.204.in-addr.arpa name = zeus-pub2.kernel.org.
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*
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* Authoritative answers can be found from:
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* 32-27.191.152.204.in-addr.arpa nameserver = ns1.kernel.org.
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* 32-27.191.152.204.in-addr.arpa nameserver = ns2.kernel.org.
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* 32-27.191.152.204.in-addr.arpa nameserver = ns3.kernel.org.
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* ns1.kernel.org internet address = 140.211.167.34
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* ns2.kernel.org internet address = 204.152.191.4
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* ns3.kernel.org internet address = 204.152.191.36
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*/
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static int print_host(const char *hostname, const char *header)
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{
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/* We can't use xhost2sockaddr() - we want to get ALL addresses,
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* not just one */
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struct addrinfo *result = NULL;
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int rc;
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struct addrinfo hint;
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memset(&hint, 0 , sizeof(hint));
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/* hint.ai_family = AF_UNSPEC; - zero anyway */
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/* Needed. Or else we will get each address thrice (or more)
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* for each possible socket type (tcp,udp,raw...): */
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hint.ai_socktype = SOCK_STREAM;
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// hint.ai_flags = AI_CANONNAME;
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rc = getaddrinfo(hostname, NULL /*service*/, &hint, &result);
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if (rc == 0) {
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struct addrinfo *cur = result;
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unsigned cnt = 0;
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printf("%-10s %s\n", header, hostname);
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// puts(cur->ai_canonname); ?
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while (cur) {
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char *dotted, *revhost;
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dotted = xmalloc_sockaddr2dotted_noport(cur->ai_addr);
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revhost = xmalloc_sockaddr2hostonly_noport(cur->ai_addr);
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printf("Address %u: %s%c", ++cnt, dotted, revhost ? ' ' : '\n');
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if (revhost) {
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puts(revhost);
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if (ENABLE_FEATURE_CLEAN_UP)
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free(revhost);
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}
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if (ENABLE_FEATURE_CLEAN_UP)
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free(dotted);
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cur = cur->ai_next;
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}
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} else {
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#if ENABLE_VERBOSE_RESOLUTION_ERRORS
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bb_error_msg("can't resolve '%s': %s", hostname, gai_strerror(rc));
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#else
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bb_error_msg("can't resolve '%s'", hostname);
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#endif
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}
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if (ENABLE_FEATURE_CLEAN_UP && result)
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freeaddrinfo(result);
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return (rc != 0);
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}
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/* lookup the default nameserver and display it */
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static void server_print(void)
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{
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char *server;
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struct sockaddr *sa;
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#if ENABLE_FEATURE_IPV6
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sa = (struct sockaddr*)_res._u._ext.nsaddrs[0];
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if (!sa)
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#endif
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sa = (struct sockaddr*)&_res.nsaddr_list[0];
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server = xmalloc_sockaddr2dotted_noport(sa);
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print_host(server, "Server:");
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if (ENABLE_FEATURE_CLEAN_UP)
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free(server);
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bb_putchar('\n');
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}
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/* alter the global _res nameserver structure to use
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an explicit dns server instead of what is in /etc/resolv.conf */
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static void set_default_dns(const char *server)
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{
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len_and_sockaddr *lsa;
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if (!server)
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return;
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/* NB: this works even with, say, "[::1]:5353"! :) */
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lsa = xhost2sockaddr(server, 53);
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if (lsa->u.sa.sa_family == AF_INET) {
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_res.nscount = 1;
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/* struct copy */
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_res.nsaddr_list[0] = lsa->u.sin;
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}
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#if ENABLE_FEATURE_IPV6
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/* Hoped libc can cope with IPv4 address there too.
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* No such luck, glibc 2.4 segfaults even with IPv6,
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* maybe I misunderstand how to make glibc use IPv6 addr?
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* (uclibc 0.9.31+ should work) */
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if (lsa->u.sa.sa_family == AF_INET6) {
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// glibc neither SEGVs nor sends any dgrams with this
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// (strace shows no socket ops):
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//_res.nscount = 0;
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_res._u._ext.nscount = 1;
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/* store a pointer to part of malloc'ed lsa */
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_res._u._ext.nsaddrs[0] = &lsa->u.sin6;
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/* must not free(lsa)! */
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}
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#endif
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}
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int nslookup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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int nslookup_main(int argc, char **argv)
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{
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/* We allow 1 or 2 arguments.
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* The first is the name to be looked up and the second is an
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* optional DNS server with which to do the lookup.
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* More than 3 arguments is an error to follow the pattern of the
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* standard nslookup */
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if (!argv[1] || argv[1][0] == '-' || argc > 3)
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bb_show_usage();
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/* initialize DNS structure _res used in printing the default
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* name server and in the explicit name server option feature. */
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res_init();
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/* rfc2133 says this enables IPv6 lookups */
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/* (but it also says "may be enabled in /etc/resolv.conf") */
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/*_res.options |= RES_USE_INET6;*/
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set_default_dns(argv[2]);
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server_print();
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/* getaddrinfo and friends are free to request a resolver
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* reinitialization. Just in case, set_default_dns() again
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* after getaddrinfo (in server_print). This reportedly helps
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* with bug 675 "nslookup does not properly use second argument"
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* at least on Debian Wheezy and Openwrt AA (eglibc based).
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*/
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set_default_dns(argv[2]);
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return print_host(argv[1], "Name:");
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}
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