import java.io.File;
public class ShowRegular
{
    public static void main(String[] args)
    {
        if(args.length == 0)
        {
            System.err.println("command-line argument required");
            System.exit(1);
        }
        String dirName = args[0];
        File f = new File(dirName);
        if(!f.exists())
        {
            System.out.printf("File %s does not exist.\n", f.getAbsolutePath());
        }
        else if(!f.isDirectory())
        {
            System.out.printf("File %s is not a directory.\n", f.getAbsolutePath());
        }
        else
        {
            File[] contents = f.listFiles();
            for(File foo : contents)
            {
                if(!foo.isDirectory())
                {
                    System.out.println(foo.getName());
                }
            }
        }
        //list all regular files in the specified directory

    }
}