/* tls.c - Trivial ls command to list regular files only. 
 */
#include <stdio.h>
#include <dirent.h>
#include <unistd.h>
#include <sys/stat.h>

int main(int argc, char *argv[])
{
    /* String to hold directory name. */
    char *dirname;

    /* Pointers needed by functions for iterating directory entries. */
    DIR *dir;
    struct dirent *entry;

    /* Struct needed for determining info about an entry with stat(). */
    struct stat statinfo;

    /* Handle command line parameter (the directory to read) if given.. */
    if (argc > 2) {
        fprintf(stderr, "Usage: %s [<directory>]\n", argv[0]);
        return 1;
    } else if (argc == 2) {
        dirname = argv[1];
    } else {
        dirname = ".";  /* default to current working directory */
    }

    /* Open the directory */
    if ((dir = opendir(dirname)) == NULL) {
        fprintf(stderr, "ERROR: Could not open directory %s\n", dirname);
        return 1;
    }

    /* Change working dir to be able to read file information. */
    chdir(dirname);

    /* Loop through all entries in the directory. */
    while ((entry = readdir(dir)) != NULL) {
        /* List regular files only. */
        stat(entry->d_name, &statinfo);
        if (S_ISREG(statinfo.st_mode)) {
            puts(entry->d_name);  /* print the name */
        }
    }

    /* Finally close the directory stream. */
    closedir(dir);
    return 0;
}