Re: [full disclosure] agile hacking?

[Valdis.Kletnieks () vt edu]

On Wed, 19 Mar 2008 17:30:08 -0000, "Petko D. Petkov" said:

> moreover, the project is not a Phrack knock-off as you said. It is
> very different. As I said, it wont contain explanations but like hands
> on tips/tricks and techniques even the most knowledgeable can learn
> from or use as a base reference.

Without an explanation of *why* a given tip/trick works, it's hard to learn from.

For example, consider the question of "Tell me how many processes called
'xyzzy' are running on a system.  The naive answer is:

% ps ax | grep xyzzy | wc -l

However, that generates an off-by-one error because it catches the grep itself.

% ps ax | grep '[x]yzzy' | wc -l

Does what you wanted - but without an understanding of *why* that regexp
doesn't match itself when the first example does, you can't apply the more
general concept of regexps that do/don't match themselves to *other* uses.
(The secret here - the second regexp is *effectively* identical to the first,
but says "look for an x next to a y" in a way that doesn't itself have an
x adjacent to a y).

So you need an explanation.

(The fact that a process can re-write its argv[0] and change the name displayed
by ps is yet another "teachable moment" - does that mean that you really want
the name it was invoked under and should add the 'ps' flag that gives that, or
do you really want the number of processes that have that modified argv value
set?  For instance, if you're using 'sendmail', there are a number of states
a given copy can be in, and you can do a status summary by counting the number
of 'accepting connections', 'rejecting connections', 'running queue' and other
similar indicators.

But again, you need an explanation.

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