nproc.c

   1 /*-
   2  * Copyright (c) 2023 Mateusz Guzik
   3  *
   4  * Redistribution and use in source and binary forms, with
   5  * or without modification, are permitted provided that the
   6  * following conditions are met:
   7  *
   8  * 1. Redistributions of source code must retain the above
   9  *    copyright notice, this list of conditions and the
  10  *    following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the
  12  *    above copyright notice, this list of conditions and
  13  *    the following disclaimer in the documentation and/or
  14  *    other materials provided with the distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
  17  * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
  18  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  20  * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  21  * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY
  22  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  23  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  24  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  25  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  26  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  28  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
  29  * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
  30  * OF SUCH DAMAGE.
  31  */
  32
  33 /*
  34  * _XOPEN_SOURCE hides _SC_NPROCESSORS_* on some BSDs
  35  */
  36 /* #define _XOPEN_SOURCE 700 */
  37
  38 #include <errno.h>
  39 #include <limits.h>
  40 #include <stdio.h>
  41 #include <stdlib.h>
  42 #include <string.h>
  43 #include <unistd.h>
  44
  45 #include <getopt.h>
  46
  47 #ifndef _SC_NPROCESSORS_CONF
  48 #error "_SC_NPROCESSORS_CONF not defined, system incompatible"
  49 #endif
  50
  51 #ifndef _SC_NPROCESSORS_ONLN
  52 #error "_SC_NPROCESSORS_ONLN not defined, system incompatible"
  53 #endif
  54
  55 static void
  56 usage(const char* progname)
  57 {
  58         fprintf(stderr, "usage: %s [-a] [-i #]\n", progname);
  59         exit(2);
  60 }
  61
  62 int
  63 main(int argc, char *argv[])
  64 {
  65         char *progname;
  66         char *endptr;
  67         int ch, all;
  68         long ignore, cpus;
  69
  70         ignore = 0;
  71         all = 0;
  72
  73         progname = argv[0];
  74         while ((ch = getopt(argc, argv, "ai:")) >= 0) {
  75                 switch (ch) {
  76                 case 'a':
  77                         all = 1;
  78                         break;
  79                 case 'i':
  80                         ignore = strtol(optarg, &endptr, 10);
  81                         if (ignore < 0 || *endptr || errno) {
  82                                 fprintf(stderr, "%s: bad ignore count: %s\n",
  83                                         progname, optarg);
  84                                 exit(2);
  85                         }
  86                         break;
  87                 default:
  88                         usage(progname);
  89                 }
  90         }
  91
  92         argc -= optind;
  93         argv += optind;
  94
  95         if (argc)
  96                 usage(progname);
  97
  98         if (all)
  99                 cpus = sysconf(_SC_NPROCESSORS_CONF);
 100         else
 101                 cpus = sysconf(_SC_NPROCESSORS_ONLN);
 102
 103         if (cpus < 0) {
 104                 fprintf(stderr, "%s: sysconf: %s", progname, strerror(errno));
 105                 exit(1);
 106         }
 107
 108         if (ignore >= cpus)
 109                 cpus = 1;
 110         else
 111                 cpus -= ignore;
 112
 113         printf("%li\n", cpus);
 114
 115         return 0;
 116 }