Thursday, June 07, 2007

Umm, What Exactly Is Google Trying To Tell Me Here?

Dear Google,

Look, I know this is a weblog about programming and Java and stuff, and I know you're just trying to help out with the targeted, "relevant" ads. And I'm okay with that. Really, I am.


I think the whole "help out the poor, socially inept Revenge of the Nerds rejects" vibe is a bit much, huh?


Kickin' it Old School: Inspecting $CLASSPATH with sed and grep

Here's a fun sed one-liner that I used today to break up the entries in my $CLASSPATH:

echo $CLASSPATH | sed 's/:/\<return>

Note that the <return> above means to actually hit the return key following the backslash. This bit of awkwardness is sed's way of specifying a literal newline as part of the substitution string (how literal can you get?). The net effect is to replace the colon characters with newlines, resulting in a display of my classpath with one entry per line.

I needed this in the context of figuring out a broken Ant build while testing some changes I'm making to JRuby. Unfortunately, even the pretty-printed version of my Ant classpath was too long to sift through with the naked eye, so I turned to grep to look for exactly what I needed:

echo $CLASSPATH | sed 's/:/\<return>
/g | grep jruby.jar'

That is, break up the classpath into one line per entry, and show me only the entries for jruby.jar. With this, I was able to determine that I had an older version of jruby.jar on my classpath that is incompatible with the current trunk. Problem solved!

I love a happy ending.