使用c++检查Linux系统硬盘空间，如果空间少于200m时删除最老的文件

下面是一个在C语言中检查Linux系统硬盘空间并删除最旧文件的示例代码：

#include <sys/statvfs.h>
#include <stdio.h>
#include <stdlib.h>
#include <dirent.h>
#include <time.h>

#define THRESHOLD 200000000

int compare(const void *a, const void *b) {
    return (*(time_t*)b - *(time_t*)a);
}

int main(void) {
    struct statvfs buf;
    if (statvfs("/", &buf) == -1) {
        perror("statvfs error");
        exit(1);
    }
    unsigned long long free_space = buf.f_bavail * buf.f_frsize;
    if (free_space < THRESHOLD) {
        DIR *dir;
        struct dirent *ent;
        dir = opendir("/");
        if (dir == NULL) {
            perror("opendir error");
            exit(1);
        }
        time_t timestamps[100];
        int i = 0;
        while ((ent = readdir(dir)) != NULL) {
            char path[100];
            sprintf(path, "/%s", ent->d_name);
            struct stat s;
            if (stat(path, &s) == -1) {
                perror("stat error");
                exit(1);
            }
            if (!S_ISREG(s.st_mode)) {
                continue;
            }
            timestamps[i++] = s.st_mtime;
        }
        closedir(dir);
        qsort(timestamps, i, sizeof(time_t), compare);
        for (int j = 0; j < i; j++) {
            char path[100];
            sprintf(path, "/%ld", timestamps[j]);
            if (remove(path) == -1) {
                perror("remove error");
                exit(1);
            }
            free_space += THRESHOLD;
            if (free_space >= THRESHOLD) {
                break;
            }
        }
    }
    return 0;
}

请注意，这仅仅是一个示例代码，实际上在生产环境中使用时需要加以修改和完善。