Coding

via XKCD

This is a bit like, if your car was built by Microsoft.

Not that I am a great programmer, but I managed to get it done in less than five minutes, including reminding myself how the modulo operation works in python.
This is from my perspective quite an interesting example on how to filter out dazzlers from a set of self proclaimed coders applying for a programming job.

Write a program that prints the numbers from 1 to 100. But for multiples of three print “Fizz” instead of the number and for the multiples of five print “Buzz”. For numbers which are multiples of both three and five print “FizzBuzz”.

Found here

I found a nice little tool in the Python Cookbook section of the Activestate website. It is pretty quick and helps to eliminate duplicate files by traversing the folder you run it on, comparing size and hashes for all the files and finally deleting them.

Comment of the author:

It ran against a 3.5 gigabyte set of files composed of about 120,000 files, of which there were about 50,000 duplicates, most of which were over 1 megabyte. The total run took about 2 minutes on a 1.33ghz G4 powerbook. Fast enough for me and fast enough without actually optimizing anything beyond the obvious.

Link to Python Recipe

Comments from my side:

- you will need python installed to use it, but you should have it anyway ;)
- as far as I can see, it works on every platform supporting python
- it doesn't replace the brain ;), it will simply delete everything duplicate
- The ASPN website is pretty slow and frequently unreachable. Contact me, if you like to have this script and can't get it from the page.

http://thedailywtf.com/Articles/The_Intentional_Slowdown.aspx

During the research for my ssh gateway project, I came across the issue, that I didn't want the ssh users to execute any commands on the gateway itself. They would still need the ability to login, since I needed the ssh connection for tunneling traffic into the private network. Discussions with a friend of mine, brought us to the idea, to replace the standard shell with something else, that stays alive, as long as the user doesn't type something specific. Afterwards it would just terminate and the ssh session will be closed.

Please welcome the "All You Can Do Is Exit" Shell.

A little bit of python did the job for me. Obviously this is depending on python being installed on your computer and there are various other ways to do this.

# cat /aycdiesh
#! /usr/local/bin/python2.4
while True:
    try:
        x = ""
        while x !="exit":
            x = raw_input("Type 'exit': ");
            if x != "exit":
                print "Only 'exit' is allowed !!";
        break;
    except KeyboardInterrupt:
        break;

Assigning the aycdiesh as a shell to the user "test", will lead to the required results.

# userinfo test
login test
passwd *
uid 1003
groups test
change NEVER
class
gecos test
dir /home/test
shell /aycdiesh
expire NEVER

Testing the login:

>ssh -l test ssh_gateway
test@ssh_gateway's password:
Last login: Wed Feb 7 11:16:40 2007 from 10.169.20.58
OpenBSD 4.0 (GENERIC) #625: Sun Sep 17 23:46:46 MDT 2006

Welcome to the ssh access gateway.

Type 'exit': dsr08tg245t243
only 'exit' is allowed !!
Type 'exit': exit
OK
Connection to ssh_gateway closed.

>

---

As always, I welcome comments to this entry, since I don't think I am a genius. Let me know, if something is wrong, or if you come up with different approaches or a better solution at all.

various

Arguments, passed to the script on the cmdline can be read with sys.argv[x]. argv[0] is the name of the script itself argv[1] the first argument and so on. Reading arguments, that have not been passed lead to an exception.

import sys
print 'argument passed has been: ' + sys.argv[1]

file operations

Files will be opened with open(filename, mode) for read and write access, while mode determines read or write.

filename="textdatei.txt"
op_mode="w"
f=open(filename, op_mode)

The name of the file and the read/write mode can be obtained from the constants name and mode.

print f.name
print f.mode

The file will be closed with close.

f.close

os operations

os.name contains the python system name. BSD returns "posix"

import os
print 'this is a ' + os.name + ' system'