import sys

def readfile(filename):
    ‘Print a file to the standard output.‘
    f=file(filename)
    while True:
        line=f.readline()
        if len(line)==0:
            break
        print line,
    f.close()

if len(sys.argv) <2:
    print ‘No action specified.‘
    sys.exit()

if sys.argv[1].startswith(‘--‘):
    option = sys.argv[1][2:]
    if option == ‘version‘:
        print ‘Version 1.2‘
    elif option ==‘help‘:
        print‘‘‘\
    This program prints files to the standard output.
    Any number of files can be specified.
    Option include:
    --version:Prints the version number
    --help:Display this help‘‘‘
    else:
        for filename in sys.argv[1:]:
            readfile(filename)

$ python cat.py
No action specified.

$ python cat.py --help
This program prints files to the standard output.
Any number of files can be specified.
Options include:
--version : Prints the version number
--help : Display this help

$ python cat.py --version
Version 1.2

$ python cat.py --nonsense
Unknown option.

$ python cat.py poem.txt
Programming is fun
When the work is done
if you wanna make your work also fun:
use Python!

>>>import sys
>>> sys.version