Sometimes I have an idea and then just wish I hadn't

[simont]

Many Unix programmers will be familiar with the utility variously called strace, truss, ktrace, dtrace and probably other names too, which logs all communication between a process and the kernel across the system call interface.

A couple of years ago I wrote an analogous program called xtruss, which produces similar logging but operates at the

Comments

Brilliant idea.

[antifuchs]

I think I could use something like this for when I have to debug interaction between various versions of Motif and the X server (and of course, our library on top of Motif). Also, thanks for pointing out xtruss, which I will install ASAP and use to try and figure out a couple of nasty bugs myself.

[gerald_duck]

Google can't trivially find a program called "subterfuge"; do you happen to have a link for it?

Just last week I wanted something that could compel a specific program to use a TCP port other than the one it had hardwired, though I'd been intending to do that at the LD_PRELOAD level.

[simont]

Subterfugue, I said. Here.

It does look pretty bit-rotted, though. "Supports Linux 2.4".

Code that writes code that writes code

[ext_822605]

It's an interesting idea to write something that works at the IPC level like that.
I once wrote something that you pass something like a Linux .so shared object and it'll write you a shim for it with the same signatures. This shim just calls the original symbols and passes through the arguments. It can then be LD_PRELOADed in front of the actual library.
Once I got that far it was easy to make the shim do arbitrary things with the calls such as API logging. What's even more interesting is that once you have that API log you can compile *that* and use it to replay the calls. This is really useful when trying to debug behaviour on, say, a production system without debugging symbols: you can capture your log and take it off for compilation on your testing systems.

Regards,
@ndy

[ext_826143]

As if you don't know this already:

Write the one-off utility, because there's guaranteed to be other people who want to do the same as you. And they might even send patches :)