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/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 1988, 1993
* The Regents of the University of California. All rights reserved.
*
* Copyright (c) 2026
* Project Tick. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#define _GNU_SOURCE 1
#include <sys/utsname.h>
#include <errno.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
static const char *progname = "domainname";
static void die_errno(const char *what) __attribute__((noreturn));
static void diex(const char *fmt, ...) __attribute__((format(printf, 1, 2),
noreturn));
static size_t linux_domainname_max(void);
static void parse_args(int argc, char *argv[], const char **domainname);
static void print_domainname(void);
static void set_domainname(const char *domainname);
static void usage(void) __attribute__((noreturn));
int
main(int argc, char *argv[])
{
const char *domainname;
const char *slash;
if (argv[0] != NULL && argv[0][0] != '\0') {
slash = strrchr(argv[0], '/');
progname = (slash != NULL && slash[1] != '\0') ? slash + 1 : argv[0];
}
parse_args(argc, argv, &domainname);
if (domainname != NULL)
set_domainname(domainname);
else
print_domainname();
return (0);
}
static void
parse_args(int argc, char *argv[], const char **domainname)
{
int ch;
opterr = 0;
while ((ch = getopt(argc, argv, "")) != -1) {
switch (ch) {
case '?':
default:
usage();
}
}
argc -= optind;
argv += optind;
if (argc > 1)
usage();
*domainname = (argc == 1) ? argv[0] : NULL;
}
static void
print_domainname(void)
{
struct utsname uts;
if (uname(&uts) != 0)
die_errno("uname");
if (fputs(uts.domainname, stdout) == EOF || fputc('\n', stdout) == EOF)
die_errno("stdout");
}
static void
set_domainname(const char *domainname)
{
size_t len;
size_t max_len;
len = strlen(domainname);
max_len = linux_domainname_max();
if (len > max_len) {
diex("domain name too long for Linux UTS namespace: %zu bytes given, "
"limit is %zu", len, max_len);
}
if (setdomainname(domainname, len) != 0)
die_errno("setdomainname");
}
static size_t
linux_domainname_max(void)
{
struct utsname uts;
return (sizeof(uts.domainname) - 1);
}
static void
die_errno(const char *what)
{
fprintf(stderr, "%s: %s: %s\n", progname, what, strerror(errno));
exit(1);
}
static void
diex(const char *fmt, ...)
{
va_list ap;
fprintf(stderr, "%s: ", progname);
va_start(ap, fmt);
vfprintf(stderr, fmt, ap);
va_end(ap);
fputc('\n', stderr);
exit(1);
}
static void
usage(void)
{
fprintf(stderr, "usage: %s [ypdomain]\n", progname);
exit(1);
}
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