usr.bin/users/users.c

   1 /*
   2  * Copyright (c) 1980, 1987, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  * @(#) Copyright (c) 1980, 1987, 1993 The Regents of the University of California.  All rights reserved.
  34  * @(#)users.c  8.1 (Berkeley) 6/6/93
  35  * $FreeBSD: src/usr.bin/users/users.c,v 1.8 2002/09/04 23:29:09 dwmalone Exp $
  36  * $DragonFly: src/usr.bin/users/users.c,v 1.5 2007/10/02 16:38:10 swildner Exp $
  37  */
  38
  39 #include <sys/types.h>
  40 #include <err.h>
  41 #include <stdio.h>
  42 #include <stdlib.h>
  43 #include <string.h>
  44 #include <unistd.h>
  45 #include <utmp.h>
  46
  47 typedef char   namebuf[UT_NAMESIZE];
  48
  49 static int scmp(const void *, const void *);
  50 static void usage(void);
  51
  52 int
  53 main(int argc, char **argv)
  54 {
  55         namebuf *names = NULL;
  56         int ncnt = 0;
  57         int nmax = 0;
  58         int cnt;
  59         struct utmp utmp;
  60         int ch;
  61
  62         while ((ch = getopt(argc, argv, "")) != -1) {
  63                 switch(ch) {
  64                 default:
  65                         usage();
  66                 }
  67         }
  68         argc -= optind;
  69         argv += optind;
  70
  71         if (!freopen(_PATH_UTMP, "r", stdin))
  72                 err(1, "can't open %s", _PATH_UTMP);
  73         while (fread((char *)&utmp, sizeof(utmp), 1, stdin) == 1) {
  74                 if (*utmp.ut_name) {
  75                         if (ncnt >= nmax) {
  76                                 nmax += 32;
  77                                 names = realloc(names,
  78                                         sizeof (*names) * nmax);
  79                                 if (names == NULL)
  80                                         err(1, "realloc");
  81                         }
  82                         strncpy(names[ncnt], utmp.ut_name, UT_NAMESIZE);
  83                         ++ncnt;
  84                 }
  85         }
  86         if (ncnt) {
  87                 qsort(names, ncnt, UT_NAMESIZE, scmp);
  88                 printf("%.*s", UT_NAMESIZE, names[0]);
  89                 for (cnt = 1; cnt < ncnt; ++cnt) {
  90                         if (strncmp(names[cnt], names[cnt - 1], UT_NAMESIZE))
  91                                 printf(" %.*s", UT_NAMESIZE, names[cnt]);
  92                 }
  93                 printf("\n");
  94         }
  95         exit(0);
  96 }
  97
  98 static void
  99 usage(void)
 100 {
 101         fprintf(stderr, "usage: users\n");
 102         exit(1);
 103 }
 104
 105 int
 106 scmp(const void *p, const void *q)
 107 {
 108         return(strncmp(p, q, UT_NAMESIZE));
 109 }