模拟linux下的ls -l命令

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

#define ERR_EXIT(m) \
    do { \
        perror(m);\
        exit(EXIT_FAILURE);\
    }while(0)

const char *statbuf_get_perms(struct stat *sbuf);
const char *statbuf_get_date(struct stat *sbuf);
const char *statbuf_get_filename(struct stat *sbuf, const char *name);
const char *statbuf_get_user_info(struct stat *sbuf);
const char *statbuf_get_size(struct stat *sbuf);

int main(int argc, const char *argv[])
{
    DIR *dir = opendir(".");
    if(dir == NULL)
        ERR_EXIT("opendir");

    struct dirent *dr;
    while((dr = readdir(dir)))
    {
        const char *filename = dr->d_name;
        if(filename[0] == '.')
            continue;

        char buf[1024] = {0};
        struct stat sbuf;
        if(lstat(filename, &sbuf) == -1)
            ERR_EXIT("lstat");

        strcpy(buf, statbuf_get_perms(&sbuf));
        strcat(buf, " ");
        strcat(buf, statbuf_get_user_info(&sbuf));
        strcat(buf, " ");
        strcat(buf, statbuf_get_size(&sbuf));
        strcat(buf, " ");
        strcat(buf, statbuf_get_date(&sbuf));
        strcat(buf, " ");
        strcat(buf, statbuf_get_filename(&sbuf, filename));

        printf("%s\n", buf);
    }

    closedir(dir);
    return 0;
}

const char *statbuf_get_perms(struct stat *sbuf)
{
    static char perms[] = "----------";
    mode_t mode = sbuf->st_mode;

    //文件类型
    switch(mode & S_IFMT)
    {
        case S_IFSOCK:
            perms[0] = 's';
            break;
        case S_IFLNK:
            perms[0] = 'l';
            break;
        case S_IFREG:
            perms[0] = '-';
            break;
        case S_IFBLK:
            perms[0] = 'b';
            break;
        case S_IFDIR:
            perms[0] = 'd';
            break;
        case S_IFCHR:
            perms[0] = 'c';
            break;
        case S_IFIFO:
            perms[0] = 'p';
            break;
    }

    //权限
    if(mode & S_IRUSR)
        perms[1] = 'r';
    if(mode & S_IWUSR)
        perms[2] = 'w';
    if(mode & S_IXUSR)
        perms[3] = 'x';
    if(mode & S_IRGRP)
        perms[4] = 'r';
    if(mode & S_IWGRP)
        perms[5] = 'w';
    if(mode & S_IXGRP)
        perms[6] = 'x';
    if(mode & S_IROTH)
        perms[7] = 'r';
    if(mode & S_IWOTH)
        perms[8] = 'w';
    if(mode & S_IXOTH)
        perms[9] = 'x';

    if(mode & S_ISUID)
        perms[3] = (perms[3] == 'x') ? 's' : 'S';
    if(mode & S_ISGID)
        perms[6] = (perms[6] == 'x') ? 's' : 'S';
    if(mode & S_ISVTX)
        perms[9] = (perms[9] == 'x') ? 't' : 'T';

    return perms;
}

const char *statbuf_get_date(struct stat *sbuf)
{
    static char datebuf[1024] = {0};
    struct tm *ptm;
    time_t ct = sbuf->st_ctime;
    if((ptm = localtime(&ct)) == NULL)
        ERR_EXIT("localtime");

    const char *format = "%b %e %H:%M"; //时间格式

    if(strftime(datebuf, sizeof datebuf, format, ptm) == 0)
    {
        fprintf(stderr, "strftime error\n");
        exit(EXIT_FAILURE);
    }

    return datebuf;
}

const char *statbuf_get_filename(struct stat *sbuf, const char *name)
{
    static char filename[1024] = {0};
    //name 处理链接名字
    if(S_ISLNK(sbuf->st_mode))
    {
        char linkfile[1024] = {0};
        if(readlink(name, linkfile, sizeof linkfile) == -1)
            ERR_EXIT("readlink");
        snprintf(filename, sizeof filename, " %s -> %s", name, linkfile);
    }else
    {
        strcpy(filename, name);
    }

    return filename;
}

const char *statbuf_get_user_info(struct stat *sbuf)
{
    static char info[1024] = {0};
    snprintf(info, sizeof info, " %3d %8d %8d", sbuf->st_nlink, sbuf->st_uid, sbuf->st_gid);

    return info;
}

const char *statbuf_get_size(struct stat *sbuf)
{
    static char buf[100] = {0};
    snprintf(buf, sizeof buf, "%8lu", (unsigned long)sbuf->st_size);
    return buf;
}