写过的奇妙代码。

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

void list(char dir[]);
void listfile(struct stat* einfo, char fname[]);
void parseParam(char arg[]);
char* mod2str(int mod);
char* num2str(unsigned int num);
char* uname(gid_t uid);
char* gname(gid_t gid);

static unsigned param = 0;
#define P_a 0b1
#define P_l 0b10
#define P_R 0b100
#define P_t 0b1000
#define P_r 0b10000
#define P_i 0b100000
#define P_s 0b1000000

int main(int argc, char* argv[]) {
    int havePath = 0;
    for (int i = 1; i < argc; i++)
        if (*argv[i] == '-')
            parseParam(argv[i]);
        else
            havePath++;
    while (--argc)
        if (**++argv != '-')
            list(*argv);
    if (!havePath)
        list(".");
    return 0;
}

void list(char dir[]) {
    // 打开目录
    DIR* dirp = opendir(dir);
    if (!dirp) {
        closedir(dirp);
        struct stat einfo;
        if (stat(dir, &einfo) == -1)
            fprintf(stderr, "zls: 无法访问 '%s': 没有那个文件或目录。\n", dir);
        else if (!(param & P_R)) {
            listfile(&einfo, dir);
            printf("\n");
        }
        return;
    }
    printf("%s:\n", dir);
    // 生成列表
    int entc, enti[PATH_MAX];
    struct entbrief {
        char name[NAME_MAX];
        time_t mtime;
    };
    struct entbrief* entv = malloc(sizeof(struct entbrief[PATH_MAX]));
    struct dirent* entp;
    for (entc = 0; (entp = readdir(dirp)) != NULL;) {
        if (!(param & P_a) && *entp->d_name == '.')
            continue;
        struct stat einfo;
        strcpy(entv[entc].name, entp->d_name);
        if (param & P_t) {
            char path[PATH_MAX];
            sprintf(path, "%s/%s", dir, entp->d_name);
            if (stat(path, &einfo) == -1)
                continue;
            entv[entc].mtime = einfo.st_mtim.tv_sec;
        }
        enti[entc] = entc;
        entc++;
    }
    // 排序
    for (int i = 1, j, temp; i < entc; i++) {
        temp = enti[i];
        for (j = i;
             // 排序的condition比较长，所以称之为“悲伤的猪大排”
             j > 0 &&
             !!(param & P_r) ^
                 (param & P_t
                      ? entv[enti[j - 1]].mtime > entv[temp].mtime
                      : strcmp(entv[enti[j - 1]].name, entv[temp].name) > 0);
             j--)
            enti[j] = enti[j - 1];
        enti[j] = temp;
    }
    // 输出
    for (int i = 0; i < entc; i++) {
        struct stat einfo;
        char path[PATH_MAX];
        sprintf(path, "%s/%s", dir, entv[enti[i]].name);
        if (stat(path, &einfo) == -1)
            continue;
        listfile(&einfo, entv[enti[i]].name);
        printf(param & P_l || i % 5 == 4 ? "\n" : "  \t");
    }
    printf(param & P_l ? "\n" : "\n\n");
    closedir(dirp);
    // 递归
    for (int i = 0; i < entc && param & P_R; i++) {
        if (!strcmp(entv[i].name, ".") || !strcmp(entv[i].name, ".."))
            continue;
        char path[PATH_MAX];
        sprintf(path, "%s/%s", dir, entv[i].name);
        list(path);
    }
    free(entv);
}

void listfile(struct stat* einfo, char fname[]) {
    if (param & P_i)
        printf("%8lu  ", einfo->st_ino);
    if (param & P_s)
        // Zhilu 纠正：应该是4KB向上取整
        printf("%4ld  ",
               (einfo->st_size / 4096 * 4) + (einfo->st_size % 4096 ? 4 : 0));
    if (param & P_l) {
        printf("%s  ", mod2str(einfo->st_mode));
        printf("%4d  ", (int)einfo->st_nlink);
        printf("%-8s  ", uname(einfo->st_uid));
        printf("%-8s  ", gname(einfo->st_gid));
        printf("%8ld  ", einfo->st_size);
        printf("%.12s  ", 4 + ctime((const time_t*)&einfo->st_mtim));
    }
    printf(S_ISDIR(einfo->st_mode) ? "\033[1;34m%-10s\033[0m" : "%-10s", fname);
}

void parseParam(char arg[]) {
#define CheckParam(ch)   \
    if (*arg == *#ch) {  \
        param |= P_##ch; \
        continue;        \
    }
    while (*++arg) {
        CheckParam(a);
        CheckParam(l);
        CheckParam(R);
        CheckParam(t);
        CheckParam(r);
        CheckParam(i);
        CheckParam(s);
        fprintf(stderr, "zls: 未知参数 '-%c'。\n", *arg);
    }
#undef CheckParam
}

char* mod2str(int mod) {
    static char str[] = "----------";
    str[0] = S_ISDIR(mod) ? 'd' : S_ISLNK(mod) ? 'l' : '-';
    str[1] = mod & S_IRUSR ? 'r' : '-';
    str[2] = mod & S_IWUSR ? 'w' : '-';
    str[3] = mod & S_IXUSR ? 'x' : '-';
    str[4] = mod & S_IRGRP ? 'r' : '-';
    str[5] = mod & S_IWGRP ? 'w' : '-';
    str[6] = mod & S_IXGRP ? 'x' : '-';
    str[7] = mod & S_IROTH ? 'r' : '-';
    str[8] = mod & S_IWOTH ? 'w' : '-';
    str[9] = mod & S_IXOTH ? 'x' : '-';
    return str;
}

char* num2str(unsigned int num) {
    static char str[NAME_MAX];
    sprintf(str, "%d", num);
    return str;
}

char* uname(gid_t uid) {
    struct passwd* pwp = getpwuid(uid);
    return pwp ? pwp->pw_name : num2str(uid);
}

char* gname(gid_t gid) {
    struct group* grp = getgrgid(gid);
    return grp ? grp->gr_name : num2str(gid);
}