Slashdot today points us to OpenSolaris, where you can now download the source for DTrace, Solaris’s super-cool tool for tracing pretty much anything you can think of.

The program interacts with the user using a compiled scripting language called “D”. This is a C-like language designed specifically for DTrace. The difference is that there are a lot of builtins, and a lot of hooks. The whole point of dtrace is that you can hook into almost any function of the operating system or another application and execute any D code at that point. The great thing is that you don’t pay for hooks you don’t use – the hooks are inserted into the executable when dtrace starts, and they are removed when it exits.

Apparently, there are like thirty thousand hooks that you can listen to. They’re in a hierarchical structure, which I don’t fully understand, but you can specify something like syscall::read:entry to trap on all read() syscalls.

D code runs in kernelspace, and it is error-checked at runtime so that you don’t accidentally crash your kernel with a bogus dtrace script.

Anyway, I think this is really cool, and it’s great that they’re open sourcing it. I’m probably going to try to get Solaris so I can fool with it… but I don’t know how much I will use it. I might not have time to do it, what with school and all.