busybox/coreutils/nice.c

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/* vi: set sw=4 ts=4: */
/*
* nice implementation for busybox
*
* Copyright (C) 2005 Manuel Novoa III <mjn3@codepoet.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <errno.h>
#include <unistd.h>
#include <sys/resource.h>
#include "busybox.h"
static inline int int_add_no_wrap(int a, int b)
{
int s = a + b;
if (b < 0) {
if (s > a) s = INT_MIN;
} else {
if (s < a) s = INT_MAX;
}
return s;
}
int nice_main(int argc, char **argv)
{
static const char Xetpriority_msg[] = "cannot %cet priority";
int old_priority, adjustment;
errno = 0; /* Needed for getpriority error detection. */
old_priority = getpriority(PRIO_PROCESS, 0);
if (errno) {
bb_perror_msg_and_die(Xetpriority_msg, 'g');
}
if (!*++argv) { /* No args, so (GNU) output current nice value. */
bb_printf("%d\n", old_priority);
bb_fflush_stdout_and_exit(EXIT_SUCCESS);
}
adjustment = 10; /* Set default adjustment. */
if ((argv[0][0] == '-') && (argv[0][1] == 'n') && !argv[0][2]) { /* "-n" */
if (argc < 4) { /* Missing priority and/or utility! */
bb_show_usage();
}
adjustment = bb_xgetlarg(argv[1], 10, INT_MIN, INT_MAX);
argv += 2;
}
{ /* Set our priority. Handle integer wrapping for old + adjust. */
int new_priority = int_add_no_wrap(old_priority, adjustment);
if (setpriority(PRIO_PROCESS, 0, new_priority) < 0) {
bb_perror_msg_and_die(Xetpriority_msg, 's');
}
}
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execvp(*argv, argv); /* Now exec the desired program. */
/* The exec failed... */
bb_default_error_retval = (errno == ENOENT) ? 127 : 126; /* SUSv3 */
bb_perror_msg_and_die("%s", *argv);
}