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 //config:config NICE
  10 //config:       bool "nice (2.3 kb)"
  11 //config:       default y
  12 //config:       help
  13 //config:       nice runs a program with modified scheduling priority.
  14
  15 //applet:IF_NICE(APPLET_NOEXEC(nice, nice, BB_DIR_BIN, BB_SUID_DROP, nice))
  16
  17 //kbuild:lib-$(CONFIG_NICE) += nice.o
  18
  19 //usage:#define nice_trivial_usage
  20 //usage:       "[-n ADJUST] [PROG ARGS]"
  21 //usage:#define nice_full_usage "\n\n"
  22 //usage:       "Change scheduling priority, run PROG\n"
  23 //usage:     "\n        -n ADJUST       Adjust priority by ADJUST"
  24
  25 #include "libbb.h"
  26
  27 int nice_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  28 int nice_main(int argc UNUSED_PARAM, char **argv)
  29 {
  30         int old_priority, adjustment;
  31
  32         old_priority = getpriority(PRIO_PROCESS, 0);
  33
  34         if (!*++argv) { /* No args, so (GNU) output current nice value. */
  35                 printf("%d\n", old_priority);
  36                 fflush_stdout_and_exit_SUCCESS();
  37         }
  38
  39         adjustment = 10;  /* Set default adjustment. */
  40
  41         if (argv[0][0] == '-') {
  42                 char *nnn = argv[0] + 1;
  43                 if (nnn[0] == 'n') { /* -n */
  44                         nnn += 1;
  45                         if (!nnn[0]) { /* "-n NNN" */
  46                                 nnn = *++argv;
  47                         }
  48                         /* else: "-nNNN" (w/o space) */
  49                 }
  50                 /* else: "-NNN" (NNN may be negative) - same as "-n NNN" */
  51
  52                 if (!nnn || !argv[1]) {  /* Missing priority or PROG! */
  53                         bb_show_usage();
  54                 }
  55                 adjustment = xatoi_range(nnn, INT_MIN/2, INT_MAX/2);
  56                 argv++;
  57         }
  58
  59         {  /* Set our priority. */
  60                 int prio = old_priority + adjustment;
  61
  62                 if (setpriority(PRIO_PROCESS, 0, prio) < 0) {
  63                         bb_perror_msg_and_die("setpriority(%d)", prio);
  64                 }
  65         }
  66
  67         BB_EXECVP_or_die(argv);
  68 }