basic_listdir.c

#include <stdio.h>
#include <stdint.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <dirent.h>

int main(int argc, char **argv)
{
    DIR *dir;
    struct dirent *entry;
    char *dirname = NULL;

    if (argc == 1)
        dirname = ".";
    else
        dirname = argv[1];

    dir = opendir(dirname);
    if (!dir) {
        fprintf(stderr, "failed to open %s\n", dirname);
        return -1;
    }

    while (entry = readdir(dir)) {
        switch (entry->d_type) {
            case DT_DIR:
                fprintf(stderr, "dir         ");
            break;
            case DT_REG:
                fprintf(stderr, "reg         ");
            break;
            default:
                fprintf(stderr, "unknown     ");
            break;
        }

        fprintf(stderr, "%s\n", entry->d_name);
    }

    closedir(dir);

    return 0;
}