uptime.cpp

/*
 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <stdio.h>

int main(int, char**)
{
    FILE* fp = fopen("/proc/uptime", "r");
    if (!fp) {
        perror("fopen(/proc/uptime)");
        return 1;
    }

    char buffer[BUFSIZ];
    auto* p = fgets(buffer, sizeof(buffer), fp);
    if (!p) {
        perror("fgets");
        return 1;
    }

    unsigned seconds;
    sscanf(buffer, "%u", &seconds);

    printf("Up ");

    if (seconds / 86400 > 0) {
        printf("%d day%s, ", seconds / 86400, (seconds / 86400) == 1 ? "" : "s");
        seconds %= 86400;
    }

    if (seconds / 3600 > 0) {
        printf("%d hour%s, ", seconds / 3600, (seconds / 3600) == 1 ? "" : "s");
        seconds %= 3600;
    }

    if (seconds / 60 > 0) {
        printf("%d minute%s, ", seconds / 60, (seconds / 60) == 1 ? "" : "s");
        seconds %= 60;
    }

    printf("%d second%s\n", seconds, seconds == 1 ? "" : "s");

    fclose(fp);
    return 0;
}