linux c++ 扫描sd卡硬盘剩余容量， 剩余容量低于10%的话，删除最早的文件，直到剩余容量高于15%

你可以使用Linux系统的statfs函数来获取文件系统的信息，包括总容量、已用空间和剩余空间等。以下是一个简单的示例代码：

#include <sys/vfs.h>
#include <iostream>

int main() {
    struct statfs diskInfo;
    if (statfs("/mnt/sdcard", &diskInfo) == -1) {
        std::cerr << "Failed to get disk info" << std::endl;
        return -1;
    }
    unsigned long long totalBytes = diskInfo.f_blocks * diskInfo.f_bsize;
    unsigned long long freeBytes = diskInfo.f_bfree * diskInfo.f_bsize;
    unsigned long long usedBytes = totalBytes - freeBytes;
    double freePercent = (double)freeBytes / totalBytes * 100;
    double usedPercent = (double)usedBytes / totalBytes * 100;
    std::cout << "Total capacity: " << totalBytes / (1024*1024) << " MB" << std::endl;
    std::cout << "Used space: " << usedBytes / (1024*1024) << " MB (" << usedPercent << "%)" << std::endl;
    std::cout << "Free space: " << freeBytes / (1024*1024) << " MB (" << freePercent << "%)" << std::endl;
    return 0;
}

你可以使用一个while循环，不断获取剩余空间并检查是否需要删除文件。如果剩余容量低于10%，则删除最早的文件，直到剩余容量高于15%。以下是一个示例代码：

#include <sys/vfs.h>
#include <sys/stat.h>
#include <dirent.h>
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>

const std::string ROOT_DIR = "/mnt/sdcard";
const double MIN_FREE_PERCENT = 10.0;
const double MAX_FREE_PERCENT = 15.0;
const int MAX_FILES_TO_DELETE = 10;

bool isDirectory(const std::string& path) {
    struct stat s;
    if (stat(path.c_str(), &s) == 0) {
        return S_ISDIR(s.st_mode);
    }
    return false;
}

void listFiles(const std::string& path, std::vector<std::string>& files) {
    DIR* dir = opendir(path.c_str());
    if (dir == nullptr) {
        return;
    }
    struct dirent* entry;
    while ((entry = readdir(dir)) != nullptr) {
        if (entry->d_name[0] == '.') {
            continue;
        }
        std::string fullPath = path + "/" + entry->d_name;
        if (isDirectory(fullPath)) {
            listFiles(fullPath, files);
        } else {
            files.push_back(fullPath);
        }
    }
    closedir(dir);
}

bool sortByLastModifiedTime(const std::string& a, const std::string& b) {
    struct stat s1, s2;
    if (stat(a.c_str(), &s1) == -1 || stat(b.c_str(), &s2) == -1) {
        return false;
    }
    return s1.st_mtime < s2.st_mtime;
}

bool deleteFile(const std::string& path) {
    return remove(path.c_str()) == 0;
}

int main() {
    while (true) {
        struct statfs diskInfo;
        if (statfs(ROOT_DIR.c_str(), &diskInfo) == -1) {
            std::cerr << "Failed to get disk info" << std::endl;
            break;
        }
        unsigned long long totalBytes = diskInfo.f_blocks * diskInfo.f_bsize;
        unsigned long long freeBytes = diskInfo.f_bfree * diskInfo.f_bsize;
        double freePercent = (double)freeBytes / totalBytes * 100;
        if (freePercent > MAX_FREE_PERCENT) {
            break;
               std::vector<std::string> files;
        listFiles(ROOT_DIR, files);
        std::sort(files.begin(), files.end(), sortByLastModifiedTime);
        int numFilesToDelete = std::min((int)files.size(), MAX_FILES_TO_DELETE);
        for (int i = 0; i < numFilesToDelete; i++) {
            if (!deleteFile(files[i])) {
                std::cerr << "Failed to delete file: " << files[i] << std::endl;
            }
            freeBytes += fileSize(files[i]);
            freePercent = (double)freeBytes / totalBytes * 100;
            if (freePercent > MAX_FREE_PERCENT) {
                break;
            }
        }
    }
    return 0;
}

在该示中，我们首先使用isDirectory函数判断一个路径是否为目录，如果目录则递归调用listFiles函数获取目录下的所有文件，并将它们存储在一个vector中。然后我们使用sortByLastModifiedTime函数将文件按照最后修改时间排序，从而删除最早的文件。最后我们使用deleteFile函数删除文件，并将释放的空间加入到剩余空间中。