Here is my little one-liner, because I used it today and I find it fun:
for f in `find .` ; do mv $f `echo $f | tr '[A-Z]' '[a-z]'` ; done
A little one-liner: rename to lowercase recursively
netcat as a logging tcp proxy
I felt I needed to write an article about netcat, so here is it !
Netcat is an incredibly usefull tool, that allows you to play with tcp connection easily from the shell.
Basically, as it name implies, it’s just cat over the network, but what its name doesn’t tell you is that it also can act as a socket listener.
So let’s play with pipes, here is one of my favourite use of netcat:
mkfifo proxypipe cat proxypipe | nc -l -p 80 | tee -a inflow | nc localhost 81 | tee -a outflow 1>proxypipe
This command will redirect traffic from localhost:80 to localhost:81, in the inflow file you while find the incoming http request, in the outfile, you will find the http response from the server.
Similarly, you can do this:
cat proxypipe | nc -l 80 | tee -a inflow | sed 's/^Host.*/Host: www.google.fr/' | nc www.google.fr 80 | tee -a outflow >proxypipe
This will allow your browser to point to google using http://localhost .
Anyway, this is my favourite but netcat has thounds of other uses, have a look at it !
It can be usefull for file transfers (gzip|nc) , performance measurement (dd|gzip), protocol debugging (replaying requests), security testing (nc does port scan) …
Installing redmine 0.8 on intrepid (ubuntu 8.10)
I’ve successfully insalled redmine pretty much easily but I needed to find out what packages to install with apt, which one with gem, which version …
Here is my magic receipe to install it all:
apt-get update apt-get install subversion mysql-server rubygems rake pwgen # next line generates a password for the database export PASSWORD=`pwgen -nc 8 1` gem install -v=2.1.2 rails echo "CREATE DATABASE redmine DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci ; GRANT ALL PRIVILEGES ON redmine.* TO 'redmine'@'localhost' IDENTIFIED BY '$PASSWORD' WITH GRANT OPTION; FLUSH PRIVILEGES" | mysql cd /opt/ svn export http://redmine.rubyforge.org/svn/branches/0.8-stable redmine-0.8 cd redmine-0.8/ cat <<EOF >> config/database.yml production: adapter: mysql socket: /var/run/mysqld/mysqld.sock database: redmine host: localhost username: redmine password: $PASSWORD encoding: utf8 EOF rake db:migrate RAILS_ENV="production" rake redmine:load_default_data RAILS_ENV="production" apt-get remove pwgen subversion RAILS_ENV="production" ./script/server
And that’s it ! Redmine is running on port 3000.
I did this on an EC2 instance and it works like a charm (ami-7cfd1a15).
Maybe next article will discuss running redmine in mongrel or apache, and creating an init script for having redmine running on boot !
HTTP’s 301 and 302
Just a little note, 301 is the HTTP code for “temporarly moved”, 302 is “permanently moved”.
Seems 302 is genereally more usefull and works better.
From what I noticed (I’m not sure about it), 302 has better SEO. Also some browsers seems to make better cache use with 302 and generating less requests on your webserver.
Hostname and underscore
RFC 952 and RFC 1123 explains the rules for choosing a hostname. I noticed recently that a lot of admins (including me) are using underscores in hostnames, but this doesn’t follow RFCs. This can lead to strange behaviours, such as mail not delivered with an RFC compliant mail server to an MX that have underscores in its name …
I noticed that because the “hostname” command on linux can set the hostname of a system, but the command doesn’t accept underscores. So guys, don’t use underscores !
MySQL “pretty printing”
I just discovered an apparently wide spread tip for mysql:
mysql> select 1, 2, 3, 4 ;
+---+---+---+---+
| 1 | 2 | 3 | 4 |
+---+---+---+---+
| 1 | 2 | 3 | 4 |
+---+---+---+---+
1 row in set (0.00 sec)
mysql> select 1, 2, 3, 4 \G;
*************************** 1. row ***************************
1: 1
2: 2
3: 3
4: 4
1 row in set (0.00 sec)
As you might have seen, the difference comes from the “\G” !
It’s very usefull when you select lot of columns that doesn’t fit the width of your terminal !
Shame on me I didn’t knew that before !
