coreutils/nice.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * nice implementation for busybox
   4  *
   5  * Copyright (C) 2005  Manuel Novoa III  <mjn3@codepoet.org>
   6  *
   7  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   8  */
   9
  10 //usage:#define nice_trivial_usage
  11 //usage:       "[-n ADJUST] [PROG ARGS]"
  12 //usage:#define nice_full_usage "\n\n"
  13 //usage:       "Change scheduling priority, run PROG\n"
  14 //usage:     "\nOptions:"
  15 //usage:     "\n        -n ADJUST       Adjust priority by ADJUST"
  16
  17 #include <sys/resource.h>
  18 #include "libbb.h"
  19
  20 int nice_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  21 int nice_main(int argc, char **argv)
  22 {
  23         int old_priority, adjustment;
  24
  25         old_priority = getpriority(PRIO_PROCESS, 0);
  26
  27         if (!*++argv) { /* No args, so (GNU) output current nice value. */
  28                 printf("%d\n", old_priority);
  29                 fflush_stdout_and_exit(EXIT_SUCCESS);
  30         }
  31
  32         adjustment = 10;  /* Set default adjustment. */
  33
  34         if (argv[0][0] == '-') {
  35                 if (argv[0][1] == 'n') { /* -n */
  36                         if (argv[0][2]) { /* -nNNNN (w/o space) */
  37                                 argv[0] += 2; argv--; argc++;
  38                         }
  39                 } else { /* -NNN (NNN may be negative) == -n NNN */
  40                         argv[0] += 1; argv--; argc++;
  41                 }
  42                 if (argc < 4) {  /* Missing priority and/or utility! */
  43                         bb_show_usage();
  44                 }
  45                 adjustment = xatoi_range(argv[1], INT_MIN/2, INT_MAX/2);
  46                 argv += 2;
  47         }
  48
  49         {  /* Set our priority. */
  50                 int prio = old_priority + adjustment;
  51
  52                 if (setpriority(PRIO_PROCESS, 0, prio) < 0) {
  53                         bb_perror_msg_and_die("setpriority(%d)", prio);
  54                 }
  55         }
  56
  57         BB_EXECVP_or_die(argv);
  58 }