c++实现：检测ubuntu系统sd卡空间使用率是否超过20%

在C++中检测Ubuntu系统的SD卡空间使用率超过20%，通常需要利用文件系统API以及标准库`<sys/statvfs.h>`来获取磁盘空间信息。以下是一个简单的示例程序：

#include <iostream>
#include <fstream>
#include <sys/statvfs.h>

bool isSpaceUsageAbove20(const char* path) {
    struct statvfs stats;
    if (statvfs(path, &stats) != 0) {
        std::cerr << "Failed to get file system statistics for " << path << ": " << strerror(errno) << '\n';
        return false;
    }

    // Calculate used space in bytes
    long long total = stats.f_blocks * stats.f_frsize;
    long long free = stats.f_bavail * stats.f_frsize;

    // Calculate and check the usage percentage
    double usage = 100.0 * ((double)(total - free)) / total;
    if (usage > 20) {
        return true;
    }

    return false;
}

int main() {
    const char* sdCardPath = "/dev/sdx"; // Replace with your SD card device path (e.g., /dev/mmcblk0p1 for a Raspberry Pi)
    bool exceeds20Percent = isSpaceUsageAbove20(sdCardPath);

    if (exceeds20Percent) {
        std::cout << "The SD card usage is over 20%." << std::endl;
    } else {
        std::cout << "The SD card usage is below or equal to 20%." << std::endl;
    }
    return 0;
}

请注意，这个示例假设路径`/dev/sdx`对应于你的SD卡设备。你需要根据实际情况替换这个路径。另外，这个例子没有处理错误，实际应用中应添加适当的错误处理。