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rcsid[] and sccsid[] and copyright[] are essentially unmaintained (and
unmaintainable).  these days, people use source.  these id's do not provide
any benefit, and do hurt the small install media
(the 33,000 line diff is essentially mechanical)
ok with the idea millert, ok dms

/*	$OpenBSD: who.c,v 1.18 2009/10/27 23:59:50 deraadt Exp $	*/
/*	$NetBSD: who.c,v 1.4 1994/12/07 04:28:49 jtc Exp $	*/

/*
 * Copyright (c) 1989, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Michael Fischbein.
 *
 * 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.
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <paths.h>
#include <pwd.h>
#include <utmp.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>
#include <err.h>
#include <locale.h>

void  output(struct utmp *);
void  output_labels(void);
void  who_am_i(FILE *);
void  usage(void);
FILE *file(char *);

int only_current_term;		/* show info about the current terminal only */
int show_term;			/* show term state */
int show_idle;			/* show idle time */
int show_labels;		/* show column labels */
int show_quick;			/* quick, names only */

#define NAME_WIDTH	8
#define HOST_WIDTH	32

int
main(int argc, char *argv[])
{
	struct utmp usr;
	FILE *ufp;
	int c;

	setlocale(LC_ALL, "");

	only_current_term = show_term = show_idle = show_labels = 0;
	show_quick = 0;
	while ((c = getopt(argc, argv, "HmqTu")) != -1) {
		switch (c) {
		case 'H':
			show_labels = 1;
			break;
		case 'm':
			only_current_term = 1;
			break;
		case 'q':
			show_quick = 1;
			break;
		case 'T':
			show_term = 1;
			break;
		case 'u':
			show_idle = 1;
			break;
		default:
			usage();
			/* NOTREACHED */
		}
	}
	argc -= optind;
	argv += optind;

	if (show_quick) {
		only_current_term = show_term = show_idle = show_labels = 0;
	}

	if (show_labels)
		output_labels();

	switch (argc) {
	case 0:					/* who */
		ufp = file(_PATH_UTMP);

		if (only_current_term) {
			who_am_i(ufp);
		} else if (show_quick) {
			int count = 0;
	
			while (fread((char *)&usr, sizeof(usr), 1, ufp) == 1) {
				if (*usr.ut_name && *usr.ut_line) {
					(void)printf("%-*.*s ", NAME_WIDTH,
						UT_NAMESIZE, usr.ut_name);
					if ((++count % 8) == 0)
						(void) printf("\n");
				}
			}
			if (count % 8)
				(void) printf("\n");
			(void) printf ("# users=%d\n", count);
		} else {
			/* only entries with both name and line fields */
			while (fread((char *)&usr, sizeof(usr), 1, ufp) == 1)
				if (*usr.ut_name && *usr.ut_line)
					output(&usr);
		}
		break;
	case 1:					/* who utmp_file */
		ufp = file(*argv);

		if (only_current_term) {
			who_am_i(ufp);
		} else if (show_quick) {
			int count = 0;

			while (fread((char *)&usr, sizeof(usr), 1, ufp) == 1) {
				if (*usr.ut_name && *usr.ut_line) {
					(void)printf("%-*.*s ", NAME_WIDTH,
						UT_NAMESIZE, usr.ut_name);
					if ((++count % 8) == 0)
						(void) printf("\n");
				}
			}
			if (count % 8)
				(void) printf("\n");
			(void) printf ("# users=%d\n", count);
		} else {
			/* all entries */
			while (fread((char *)&usr, sizeof(usr), 1, ufp) == 1)
				output(&usr);
		}
		break;
	case 2:					/* who am i */
		ufp = file(_PATH_UTMP);
		who_am_i(ufp);
		break;
	default:
		usage();
		/* NOTREACHED */
	}
	exit(0);
}

void
who_am_i(FILE *ufp)
{
	struct utmp usr;
	struct passwd *pw;
	char *p;
	char *t;

	/* search through the utmp and find an entry for this tty */
	if ((p = ttyname(0))) {
		/* strip any directory component */
		if ((t = strrchr(p, '/')))
			p = t + 1;
		while (fread((char *)&usr, sizeof(usr), 1, ufp) == 1)
			if (*usr.ut_name && !strcmp(usr.ut_line, p)) {
				output(&usr);
				return;
			}
		/* well, at least we know what the tty is */
		(void)strncpy(usr.ut_line, p, UT_LINESIZE);
	} else
		(void)strncpy(usr.ut_line, "tty??", UT_LINESIZE);

	pw = getpwuid(getuid());
	(void)strncpy(usr.ut_name, pw ? pw->pw_name : "?", UT_NAMESIZE);
	(void)time(&usr.ut_time);
	*usr.ut_host = '\0';
	output(&usr);
}

void
output(struct utmp *up)
{
	struct stat sb;
	char line[sizeof(_PATH_DEV) + sizeof (up->ut_line)];
	char state = '?';
	static time_t now = 0;
	time_t idle = 0;

	if (show_term || show_idle) {
		if (now == 0)
			time(&now);
		
		memset(line, 0, sizeof line);
		strlcpy(line, _PATH_DEV, sizeof line);
		strlcat(line, up->ut_line, sizeof line);

		if (stat(line, &sb) == 0) {
			state = (sb.st_mode & 020) ? '+' : '-';
			idle = now - sb.st_atime;
		} else {
			state = '?';
			idle = 0;
		}
		
	}

	(void)printf("%-*.*s ", NAME_WIDTH, UT_NAMESIZE, up->ut_name);

	if (show_term) {
		(void)printf("%c ", state);
	}

	(void)printf("%-*.*s ", UT_LINESIZE, UT_LINESIZE, up->ut_line);
	(void)printf("%.12s ", ctime(&up->ut_time) + 4);

	if (show_idle) {
		if (idle < 60) 
			(void)printf("  .   ");
		else if (idle < (24 * 60 * 60))
			(void)printf("%02d:%02d ", 
				     (idle / (60 * 60)),
				     (idle % (60 * 60)) / 60);
		else
			(void)printf(" old  ");
	}
	
	if (*up->ut_host)
		printf("  (%.*s)", HOST_WIDTH, up->ut_host);
	(void)putchar('\n');
}

void
output_labels(void)
{
	(void)printf("%-*.*s ", NAME_WIDTH, UT_NAMESIZE, "USER");

	if (show_term)
		(void)printf("S ");

	(void)printf("%-*.*s ", UT_LINESIZE, UT_LINESIZE, "LINE");
	(void)printf("WHEN         ");

	if (show_idle)
		(void)printf("IDLE  ");

	(void)printf("  %.*s", HOST_WIDTH, "FROM");

	(void)putchar('\n');
}

FILE *
file(char *name)
{
	FILE *ufp;

	if (!(ufp = fopen(name, "r"))) {
		err(1, "%s", name);
		/* NOTREACHED */
	}
	return(ufp);
}

void
usage(void)
{
	(void)fprintf(stderr, "usage: who [-HmqTu] [file]\n       who am i\n");
	exit(1);
}