source: MondoRescue/branches/2.2.2/mindi-busybox/coreutils/nice.c@ 1247

/* 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');
        }
    }

    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);
}