Alternative implementation for the UNIX ls command.

myls.c

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

void print_permissions(struct stat s);
void print_modified(struct stat s);
void print_owner(struct stat s);
void print_group(struct stat s);

int main(int argc, char* argv[])
{
    DIR *dir;
    struct dirent *file;
    struct stat st;

    dir = opendir(argv[1]);
    while ((file = readdir(dir)) != NULL) {
        stat(file->d_name, &st);    

        print_permissions(st);
        printf(" %3u", st.st_nlink);
        print_owner(st);
        print_group(st);
        printf(" %10lld", st.st_size);
        print_modified(st);
        printf(" %s\n", file->d_name);
    }
    closedir(dir);
}


void print_owner(struct stat s)
{
    struct passwd *pw = getpwuid(s.st_uid);
    printf(" %s ", pw->pw_name);
}

void print_group(struct stat s)
{
    struct group *gr = getgrgid(s.st_gid);
    printf(" %s ", gr->gr_name);
}

void print_permissions(struct stat s)
{
    printf((S_ISDIR(s.st_mode)) ? "d" : "-");
    printf((s.st_mode & S_IRUSR) ? "r" : "-");
    printf((s.st_mode & S_IWUSR) ? "w" : "-");
    printf((s.st_mode & S_IXUSR) ? "x" : "-");
    printf((s.st_mode & S_IRGRP) ? "r" : "-");
    printf((s.st_mode & S_IWGRP) ? "w" : "-");
    printf((s.st_mode & S_IXGRP) ? "x" : "-");
    printf((s.st_mode & S_IROTH) ? "r" : "-");
    printf((s.st_mode & S_IWOTH) ? "w" : "-");
    printf((s.st_mode & S_IXOTH) ? "x" : "-");
}

void print_modified(struct stat s)
{
    struct tm lt;
    localtime_r(&s.st_mtime, &lt);
    char timbuf[80];
    strftime(timbuf, sizeof(timbuf), "%b %d %H:%M", &lt);

    printf(" %s",   timbuf);
}