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/* getcanon.c - Print the canonical name of a host, default to localhost.
*
* This code is Copyright (c) 2012, by the authors of nmh. See the
* COPYRIGHT file in the root directory of the nmh distribution for
* complete copyright information.
*/
#include <netdb.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
#include <limits.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
int
main(int argc, char *argv[])
{
char buf[_POSIX_HOST_NAME_MAX + 1];
const char *hostname;
struct addrinfo hints, *res;
/* Borrowed the important code below from LocalName() in sbr/mts.c. */
if (argc > 2) {
fprintf(stderr, "usage: %s [hostname]\n", argv[0]);
return 1;
}
if (argc == 2)
hostname = argv[1];
else {
/* First get our local name. */
if (gethostname(buf, sizeof buf)) {
fprintf(stderr, "gethostname() failed: %s\n", strerror(errno));
return 1;
}
hostname = buf;
}
/* Now fully qualify the hostname. */
memset(&hints, 0, sizeof hints);
hints.ai_flags = AI_CANONNAME;
hints.ai_family = AF_UNSPEC;
if (getaddrinfo(hostname, NULL, &hints, &res)) {
puts(hostname);
return 1;
}
puts(res->ai_canonname);
return 0;
}
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