import os
import sys

# Let wd be the current working directory
#
# Example usage:
# 
# "python ls"
#     Prints the contents of wd
# "python ls dir"
#     Prints the contents of wd/dir
# "python ls dir subdir subsubdir ..."
#     Prints the contents of wd/dir/subdir/subsubdir
#
#
# Example output:
#
# $ python ls     # note that the order is undefined
# dir
# myfile.txt
# dir1

def main():
    # Get target directory
    dir_name = parse_args()

    # Get contents of target
    contents = os.listdir(dir_name)
    
    # Print contents of target
    print_contents(contents)


def parse_args():
    '''
    Returns the first argument passed to the function
    at the command line, or the current directory if no such
    arg was passed.
    '''
    
    # argv[0] is the name of this script, so we ignore it.
    args = sys.argv[1:]
    
    if len(args) == 0:
        return os.getcwd()

    path = ""
    for token in args:
        path = os.path.join(path, token)
    return path
    

def print_contents(contents):
    '''
    Prints the elements of contents, one per line. The order is
    undefined.
    '''
    for item in contents:
        print item
        

if __name__  == '__main__':
    main()