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system last boot, in C

Name: Anonymous 2007-04-07 17:07 ID:X+5rb0Y3

i'm programming in C to output the time of the system's last boot (linux).

can't read from /var/log/ since i don't have permission.

halp plz.

Name: Anonymous 2007-07-27 20:33 ID:D++yz7Yp

/*
 *  lastboot.c
 *
 *  $Id: lastboot.c,v 1.00 2007/07/28 01:30:00 prog Exp $
 *
 *  Copyright (C) 2007 by 4chan's /prog/ <http://dis.4chan.org/prog/>;
 *
 *  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 3 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, see <http://www.gnu.org/licenses/>;.
 */

#include <stdio.h>
#include <time.h>

int main(void)
{
        int uptime, ret;
        time_t t;
        FILE * f;

        f = fopen("/proc/uptime","r");
        if (!f)
        {
                perror("cannot open /proc/uptime");
                return 1;
        }

        ret = fscanf(f, "%u", &uptime);
        if (ret==EOF)
        {
                perror("cannot read /proc/uptime");
                return 2;
        }
        if (ret!=1)
        {
                puts("/proc/uptime has bad format");
        }

        fclose(f);

        t = time(0)-uptime;
        printf("System last booted: %s\n", ctime(&t));

        return 0;
}

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