/*-
* Copyright (c) 2017 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Christos Zoulas.
*
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
*/

#include <stdio.h>
#include <stdlib.h>
#include <err.h>
#include <sys/sysctl.h>

static int
getprocpath(char *path, size_t len, pid_t pid)
{
       const int name[] = {
           CTL_KERN, KERN_PROC_ARGS, pid, KERN_PROC_PATHNAME,
       };
       return sysctl(name, __arraycount(name), path, &len, NULL, 0);
}

int
main(int argc, char *argv[])
{
       if (argc != 2) {
               fprintf(stderr, "Usage: %s <pid>\n", getprogname());
               return EXIT_FAILURE;
       }

       char buf[MAXPATHLEN];
       pid_t pid = atoi(argv[1]);

       if (getprocpath(buf, sizeof(buf), pid) == -1)
               err(EXIT_FAILURE, "sysctl: %d", pid);
       printf("%s\n", buf);
       return EXIT_SUCCESS;
}