Escaping Single-Quotes in sed

This is a just a re-post of this excellent article by Stuart Coleville:

Using single quotes in BASH ensures that the shell doesn’t expand the contents of the quoted string and this is useful most of the time. However if you want to use single quotes within a single quoted string things don’t work out as you might expect.

If I want to use sed to match some text with a single quotes in it, I will run into trouble if I run:

sed 's/user \= 'root/user \= 'moi/g'

Alternatively if I run (on the same snippet):

sed 's/user \= \'root/user \= \'moi/g'

I will get:

/bin/bash: -c: line 1: unexpected EOF while looking for matching `''
/bin/bash: -c: line 2: syntax error: unexpected end of file

This doesn’t work because the escaped single-quotes (\') are not expanded and are therefore treated literally.

To single quotes work you need to break out of the single quoted string then escape your single quote. Like so:

sed 's/user \= '\''root/user \= '\''moi/g'

Because \' is not inside of single quotes the single-quote is properly escaped and the output is as we’d expect:

user = 'root' ->  user = 'moi'

In conclusion, the title of this post is a bit of a misnomer. You actually can’t put single quotes inside of a single-quoted string. However breaking out allows us to get to where we want to be.

Installing Amazon EC2 tools to Debian Lenny

I was reading through Bill Childers excellent article in Linux Journal on running Ubuntu under EC2 and I thought I add my notes on how to make the client tools run on Debian.

First, install the Sun JDK (see my previous post on how to do that).

With that done, download the tools from this page:

AWS Developer Community

Or simply by using this link:

ec2-api-tools.zip

Next, unzip them.

Then create a configuration file to export the proper environment variables when your shell fires up:

$ vi ~/.ec2.conf
Add the lines:

export EC2_CERT=whereveryourx509lives/cert-whatever-x509.pem
export EC2_PRIVATE_KEY=whereveryourx509pklives/pk-whatever-x509.pem
export JAVA_HOME=/usr/lib/jvm/java-6-sun/jre
export EC2_HOME=whereveryourec2toolswererunzipped

Save it.

Now add this to the bottom of your .bashrc:

. ~/.ec2.conf
Start a new shell and test for the var's using:

$ export | grep EC2
if they're there, you're all set.

Now test by cd'ing into your ec2 tools bin folder and running:

ec2-describe-images -o self -o amazon
If you get a huge java stack trace, changes are your jdk isn't installed properly.

Otherwise, you should get a very long list of all the amazon AMI's available to run from.

Installing the JDK to Debian Lenny

The first thing to keep in mind is that Debian tries with all its might to remain free and open. In that regard, it resists including proprietary packages - even popular ones - in its main repositories.

So to give debian access to everything, you need to edit your

/etc/apt/source.list

use the following command in vi to include the contrib and non-free packages in your configured repositories:

:%s/main/main contrib non-free/g

:wq

For the sake of being thorough, run

# apt-get update

then

# apt-get install sun-java6-jdk

Answer in the affirmative to the various prompts.

When you're complete, adjust your alternatives like so:

#update-java-alternatives -s java-6-sun

et voila

Finding Installed Ruby Lib's

Since I can't seem to escape ruby, it would seem prudent to start documenting how to pick it apart.

Here's a little one-liner I just picked up apropos of puppet that tells you whether a lib is present:

# ruby -r -e "puts :installed"

If it's there, you'll see "installed". If not, something like "no such package".