Author Archive

« Older Entries

Treetop: Grammar’s Cool

Released February 12th, 2008

Treetop was one of the more exciting projects I saw at last year’s RubyConf. Nathan Sobo’s Treetop talk is available online and I urge you to watch it. Nathan did a great job of explaining the basics of syntactic analysis, and then got into the specifics of using Treetop’s implementation of parsing expression grammars to put the concepts to work.

Treetop appeared to gather all the concepts together into an understandable domain specific language. All of the tokenization and node structure can go into a single file, and the interactive nature of Ruby makes for the perfect sand box. I felt like I could get somewhere if I invested just an hour into this. I was happy to find that my impressions were correct.

After a short time I had caught on enough to start writing my own code. Once over the hump the rest was easy. I was able to write and test a Treetop grammar for parsing CSV files within a few hours. I chose CSV parsing because I was already familiar with the format, and I could compare my implementation to not just one but two existing Ruby libraries.
(more…)

Posted in Web Development | No Comments »
Tagged:

‘cvs update: move away foo.bar; it is in the way’

Released April 26th, 2007

A client site still uses cvs, the ever trusty version control system. After what seemed a run of the mill merge I noticed this:

C lib/jt400_3_3.jar
cvs update: move away lib/jt400_3_3.jar; it is in the way

Very peculiar. That file hadn’t changed on the branch. I googled around and an explanation started to come together.

First, from the always excellent Roedy Green’s Java & Internet Glossary on Mindprod:

CVS is disturbed by the appearance of repository files it did not put there. Your best bet is simply to delete the entire directory containing the offending file by hand, and re checkout or reupdate the directory to build the necessary entries. Then you can add the files safely.

Then, I found this mailing list post:

This means the file that CVS wants to checkout exists on the local machine but CVS never created the file in the past. This it isn’t CVS’s file and it complains rather than blindly overwriting.

The solution everywhere was the same: just blow away the directory and check it out again. Worked for me. Now I need to puzzle out how it happened in the first place…

Posted in System Administration | 2 Comments »
Tagged:

rails fixtures with models using set_table_name

Released April 22nd, 2007

If you have a model that uses set_table_name you may hit a snag when trying to use fixtures and unit tests. The solution is twofold: name the fixture file using the legacy table name, and use the set_fixture_class method in your unit test. I coudn’t find this method mentioned in Agile Web Development with Rails, and there’s only a brief mention on the rubyonrails.com site. Still, some web searches turned up the answers.

Here is a simple example:

(more…)

Posted in Systems Integration | 2 Comments »
Tagged:

Hibernate and your Getters and Setters

Released March 11th, 2007

When you’re using Hibernate and are mapping to properties, keep your getters and setters as simple and self-contained as possible. The receiver being initialized may not have any other properties set, and the value being passed may not be fully initialized yet, either.

If you don’t respect these two possibilities, then you will get bit in the butt alot, when you least expect it. To be fair, these situations can happen whether you’re using Hibernate or not, but when we first started using the framework we made lots of assumptions.

Here is a completely ridiculous example that violates the above restrictions:
(more…)

Posted in Software Development | 3 Comments »
Tagged:

Slides for “You’ll Be Seeing Ruby”

Released May 17th, 2006

The slides for the presentation are finally available, along with a zipfile, on the Presentation: You’ll Be Seeing Ruby page.

It’s been a month now since our last performance, but it all comes back every time I look at the slides.

Posted in Software Development | No Comments »
Tagged:

managing disk space with logrotate

Released April 26th, 2006

At a customer site, the test and production linux servers for some intranet applications were slowly running out of disk space. The apps themselves were running fine, it was the logfiles generated by the apps that were the issue; logging that came in useful just in case something went wrong, but quickly aged. In one particular case, a catalina.out file was several years old and was 11 gigabytes; 90% of it wasn’t really relevant any longer.

The solution to the problem of wrangling logfiles is probably already installed on your server: it’s logrotate. Chances are logrotate is already configured in your system crontab as a daily task, and chances are it is configured to obey any configuration files found in the /etc/logrotate.d directory. If you find that directory, you are probably good to go.

(more…)

Posted in System Administration | 1 Comment »
Tagged:

accessing as400 databases with Ruby, Java, and the RubyJavaBridge

Released April 24th, 2006

iSeries systems and Ruby are separate universes right now; I know of no native Ruby way to connect to an AS400 system. However, with the help of Java we can bridge the gap.

Probably the simplest example is connecting to an iSeries system using JDBC to select from some tables, and with the right libraries it is straightforward. It’s also fun to be doing some nifty quick Ruby but with some preexisting and proven Java libraries.

Also, if you use Java and Ruby, definitely put arton’s RubyJavaBridge in your pocket; you’ll end up using it more than once.

What you’ll need:

  • Ruby (well yea)
  • Java (ok)
  • access to an AS400 system (that’s the whole point here…)
    For testing, I’ve been using a free account available from Holger Scherer Software und Beratung.
  • jt400.jar jdbc drivers from JTOpen, a great open-source Java library for AS400 access.
  • RubyJavaBridge is the keystone for this.

Installing the software is the hardest part of this exercise, but it’s more tedium than anything. Once you’ve got it all downloaded and running the fun can begin.

(more…)

Posted in System Administration | 9 Comments »
Tagged:

Seeing Ruby

Released April 5th, 2006

This past Friday I participated in my first presentation, Seeing Ruby: An Introduction to the Ruby Programming Language at the iTRC in Louisville, Kentucky. Chuck Fouts, Steven Yelton, and I did our level best to introduce our audience to one of our favorite development tools. Our audience was fantastic, and had lots of questions. Everyone stayed a good 15 minutes after the official end to finish Steven’s awesome Rails demo.

Honestly, Ruby sells itself though. People tend to sit up and notice blocks and open classes.

We’ll be posting the presentation slides very soon to the permanent page. And as we take the show to other venues we’ll be tweaking and refining the content. Initial feedback is to beef up the handout with a cheatsheet of language features; our whirlwind tour of the language goes by quickly and some sort of reference will help keep everything together.

Our audience expressed great interest in Ruby on Rails and AJAX, even a few requests for some Seeing More Ruby classes. We’re debating on whether “You’ll Be Seeing AJAX” or “You’ll Be Seeing Rails” next. :) Let us know which you’d rather see.

Incidentally, we’re also taking this presentation to a company for a private show, and we’d be willing to come talk with you and your colleagues as well. Just contact us!

Posted in Software Development | 2 Comments »
Tagged:

cvs history

Released February 22nd, 2006

For alot of people, CVS is history; they’ve switched to SVN and are loving life. For those of us continuing the use this venerable tool, I present the following cobbled together bit of utility.

It’s a bash function. and a nice way to keep an eye on what’s happening on a cvs repository. I work with a team of around 7 guys, and I like to keep an eye on what’s changed and who changed it.

It works like this, summarizing what I consider to be the highlights from the cvs history command, and defaults to showing checkins for the current date:

$ cvshist
M 2006-02-22 10:34 EDT jsmith  1.3  InternalOperation.java         APRJ7A/src/com/ppc/oepica/model/internal
M 2006-02-22 10:53 EDT jsmith  1.37 FooBarCopier.java              APRJ7A/src/com/ppc/oepica/model/external
M 2006-02-22 11:26 EDT darrend 1.23 CommonJobBase.java             APRJ7A/src/com/ppc/oepica/model/common

I use the date command, which gives me some flexibility when specifying a date

$ cvshist yesterday
$ cvshist 2 days ago
$ cvshist january 10
$ cvshist 2006-01-11

Here’s the source. I’ve used this on linux and cygwin; you’ll need bash, gnu date, and cvs.

$ declare -f
cvshist ()
{
  export CVSROOT=:pserver:darrend@shlnxtest1:/home/cvs;
  TARGET_DATE=$(date -d "$*" +%Y-%m-%d);
  cvs history -a -z EDT -c -D $TARGET_DATE | sed "s/\s*==.*$//" | grep "$TARGET_DATE"
}

Posted in System Administration | No Comments »
Tagged:

quick and dirty ruby

Released February 16th, 2006

At work I received an email from someone that listed libraries I should use when connecting to their AS400 system. I wanted a quick way to convert their whitespace table into a nice comma-separated list. Below is the first 6 lines from about 50 or so.

Sequence
 number   Library
    10    QTEMP            

    20    DDMFLIB2
....

If it’s computable but a one-off, I immediately go to Ruby nowadays. 10 years ago it would have been Perl, 15 or 20 years ago the choice would have been probably a meld of sed|awk.

I always go with __END__ in these situations; Ruby stops processing at the __END__ line, but you are given an enumerable access to the contents that follow with the magical DATA object.

matches = DATA.collect { |line| line.match(/\\s+\\d+\\s+(\\w+)/) }
matches.compact!
puts matches.collect { |match| match[1] }.join(', ')

__END__
Initial library list:                            

Sequence
 number   Library
    10    QTEMP            

    20    DDMFLIB2
    30    APPSDEV
    50    FILES2                                                       

   110    QRPG

Let’s try it out (running Ruby/Windows in a Cygwin terminal):

dday@xpmachine21 ~
$ ruby liblist.rb
QTEMP, DDMFLIB2, APPSDEV, FILES2, QRPG

Success!

Posted in Web Development | 2 Comments »
Tagged:

« Older Entries