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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> /* for getaddrinfo */
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h> /* for gethostname */
#include <limits.h> /* for _POSIX_HOST_NAME_MAX */
#include <string.h> /* for memset */
#include <stdio.h>
#include <errno.h>
int
main(int argc, char *argv[])
{
char buf[_POSIX_HOST_NAME_MAX + 1];
const char *hostname = buf;
struct addrinfo hints, *res;
int status = 0;
/* Borrowed the important code below from LocalName() in sbr/mts.c. */
if (argc < 2) {
/* First get our local name. */
status = gethostname(buf, sizeof buf);
} else if (argc == 2) {
hostname = argv[1];
} else if (argc > 2) {
fprintf(stderr, "usage: %s [hostname]\n", argv[0]);
return 1;
}
if (status == 0) {
/* Now fully qualify the hostname. */
memset(&hints, 0, sizeof hints);
hints.ai_flags = AI_CANONNAME;
hints.ai_family = AF_UNSPEC;
if ((status = getaddrinfo(hostname, NULL, &hints, &res)) == 0) {
printf("%s\n", res->ai_canonname);
freeaddrinfo(res);
} else {
printf("%s\n", hostname);
}
} else {
fprintf(stderr, "gethostname() failed: %s\n", strerror(errno));
}
return status;
}
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