Answer to problem 24 from Project Euler. Python is the programming language of choice for this problem too.
#!/usr/bin/env python
# Project Euler problem 24
import itertools
newlist = list(map("".join, itertools.permutations('0123456789')))
print newlist[999999]
Solution to problem 29 from Project Euler. Also written in Python as my previous post.
#!/usr/bin/env python
# Project Euler problem 29
list = []
for a in range(2, 101):
for b in range(2, 101):
product = a ** b
list.append(product)
list.sort()
newlist = sorted(set(list))
print len(newlist)
Below is the solution to problem 30 from Project Euler. It’s written in Python, a programming language I’m trying to learn.
#!/usr/bin/env python
# Project Euler problem 30
narc_sum = 0
for number in range(100, 200000):
# Transform the number into a string
string = str(number)
# Transform the string into a list
lst = list(string)
sum = 0
for i in range(len(lst)):
# Add the members of the list to the fifth power
sum = sum + (int(lst[i])**5)
if (number == sum):
# Add all numbers and store in narc_sum value
narc_sum = narc_sum + number
print "Sum is ",narc_sum
So the other day I was looking around and discovered the notify-send command. It basically sends notifications to the desktop. Pretty useful now adays.
[11:49:13] xavi@thinkpad: ~ $ sudo dpkg -S `which notify-send`
libnotify-bin: /usr/bin/notify-send
[11:49:15] xavi@thinkpad: ~ $
It is installed with libnotify-bin via aptitude.
[11:50:35] xavi@thinkpad: ~ $ sudo aptitude install libnotify-bin
So, once installed lets create a practical script. On my job I need to have a permanente VPN connection. Once in a while the VPN connection drops and we have to connect again. Lets create a simple script that notifies us when the connection drops.
#!/bin/bash
# Check tunnel interface
while "true"; do
/sbin/ifconfig tun0 &> /dev/null
while [ $? -ne 0 ]; do
notify-send -t 5000 "VPN" "VPN is down"
done
sleep 300
done
We save and copy the script, give it execution permissions with chmod and send it to background.
[11:55:47] xavi@thinkpad: ~ $ chmod +x /tmp/check-vpn.sh; /tmp/check-vpn.sh &
[1] 15613
[12:00:43] xavi@thinkpad: ~ $
Here is a screenshot of it working.
Enjoy.
So lets say you want to see how many established connections we have on a particular port/service. Most of the people would use netstat, however I prefer ss.
On a Debian based system ss can be installed with the iproute package.
user@server: ~ $ sudo dpkg -S `which ss` iproute: /sbin/ss user@server: ~ $
On a Red Hat based system it will be installed with iproute too.
[user@redhat ~]# sudo rpm -qf `which ss` iproute-2.6.18-11.el5 [user@redhat ~]#
aptitude install iproute and yum install iproute will install the package on a Debian and Red Hat system respectively.
Now lets show some examples. Lets say we want to see how many established ssh connections there are.
[user@redhat ~]# sudo ss -t '( sport = :22 )' State Recv-Q Send-Q Local Address:Port Peer Address:Port ESTAB 0 0 ::ffff:10.40.7.12:ssh ::ffff:10.16.241.194:56325 ESTAB 0 0 ::ffff:10.40.7.12:ssh ::ffff:10.16.241.194:53804 ESTAB 0 0 ::ffff:10.40.7.12:ssh ::ffff:10.16.241.194:60486 ESTAB 0 0 ::ffff:10.40.7.12:ssh ::ffff:10.14.17.48:37471 ESTAB 0 0 ::ffff:10.40.7.12:ssh ::ffff:10.16.241.194:57982 ESTAB 0 0 ::ffff:10.40.7.12:ssh ::ffff:10.16.241.194:57525 ESTAB 0 304 ::ffff:10.40.7.9:ssh ::ffff:10.14.17.22:46376 ESTAB 0 0 ::ffff:10.40.7.9:ssh ::ffff:10.16.241.28:42654 ESTAB 0 0 ::ffff:10.40.7.9:ssh ::ffff:10.16.241.12:36276 ESTAB 0 0 ::ffff:10.40.7.9:ssh ::ffff:10.16.241.8:57936 ESTAB 0 0 ::ffff:10.40.7.9:ssh ::ffff:10.16.241.28:42855 [user@redhat ~]#
-t displays all TCP sockets
You can also substitute the port number by the name of the service that runs in it by default.
user@debian:~$ sudo ss -t '( sport = :mysql )' State Recv-Q Send-Q Local Address:Port Peer Address:Port ESTAB 0 0 192.168.140.121:mysql 192.168.137.234:35512 user@debian:~$
To see all opened ports on the server use the -a option.
xavi@linode2:~$ sudo ss -t -a State Recv-Q Send-Q Local Address:Port Peer Address:Port LISTEN 0 5 *:nrpe *:* LISTEN 0 50 192.168.140.121:mysql *:* LISTEN 0 8 *:pop3 *:* LISTEN 0 8 *:imap2 *:* LISTEN 0 128 :::www :::* LISTEN 0 128 *:ssh *:* LISTEN 0 128 :::ssh :::* LISTEN 0 100 *:smtp *:* LISTEN 0 128 :::https :::* TIME-WAIT 0 0 ::ffff:173.255.231.252:www ::ffff:79.158.142.28:55032 ESTAB 0 0 192.168.140.121:mysql 192.168.137.234:35512 ESTAB 0 48 173.255.231.252:ssh 79.158.142.28:48395 TIME-WAIT 0 0 ::ffff:173.255.231.252:www ::ffff:79.158.142.28:55033 TIME-WAIT 0 0 ::ffff:173.255.231.252:www ::ffff:173.255.231.252:37223 xavi@linode2:~$
I believe ss command is simpler to use but less known than netstat. Enjoy.