14.c

#include <dirent.h>
#include <fcntl.h>
#include <grp.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>

void printInfo(struct stat *filestat, const char *fileName);

int main(int argc, char **argv)
{
    FILE *         file;
    DIR *          dir;
    struct dirent *dirent;
    struct stat    filestat;
    if (fopen("output.txt", "r") == NULL) {
        unlink("output.txt");
    }
    if (argc < 2) {
        dir = opendir(".");
        if (dir == NULL) {
            perror("Error ");
        }
    }
    if (argc >= 2) {
        dir = opendir(argv[1]);
        if (dir == NULL) {
            perror("Error ");
        }
    }
    while ((dirent = readdir(dir)) != NULL) {
        if ((strncmp(dirent->d_name, ".", 2) == 0) || (strncmp(dirent->d_name, "..", 2) == 0)) {
            continue;
        }

        if ((file = fopen(dirent->d_name, "r")) || dirent != NULL) {
            lstat(dirent->d_name, &filestat);
            if (freopen("output.txt", "a", stdout) == NULL) {
                perror("freopen() failed");
                exit(-1);
            }
            printInfo(&filestat, dirent->d_name);
        }
        else {
            perror("Error ");
        }
    }
    return EXIT_SUCCESS;
}
void printInfo(struct stat *filestat, const char *fileName)
{
    struct passwd *pwd;
    struct group * grp;
    char           f_created_time[50];

    grp = getgrgid(filestat->st_gid);
    pwd = getpwuid(filestat->st_uid);
    struct tm c_time;
    c_time = *localtime(&filestat->st_ctime);
    strftime(f_created_time, sizeof(f_created_time), "%b %2d %R", &c_time);

    printf((S_ISDIR(filestat->st_mode)) ? "d" : "-");
    printf((filestat->st_mode & S_IRUSR) ? "r" : "-");
    printf((filestat->st_mode & S_IWUSR) ? "w" : "-");
    printf((filestat->st_mode & S_IXUSR) ? "x" : "-");
    printf((filestat->st_mode & S_IRGRP) ? "r" : "-");
    printf((filestat->st_mode & S_IWGRP) ? "w" : "-");
    printf((filestat->st_mode & S_IXGRP) ? "x" : "-");
    printf((filestat->st_mode & S_IROTH) ? "r" : "-");
    printf((filestat->st_mode & S_IWOTH) ? "w" : "-");
    printf((filestat->st_mode & S_IXOTH) ? "x" : "-");
    printf(" ");

    printf("%2lu %14.32s %14.32s %8ld %12.14s %s\n", filestat->st_nlink, pwd->pw_name, grp->gr_name,
           filestat->st_size, f_created_time, fileName);
}