Re: apt debug
On Mon, 13 Oct 2025, The Wanderer wrote:
> On 2025-10-13 at 10:34, fxkl47BF@protonmail.com wrote:
>
>> On Mon, 13 Oct 2025, Greg Wooledge wrote:
>>
>>> On Mon, Oct 13, 2025 at 13:07:37 +0000, fxkl47BF@protonmail.com wrote:
>
>>>> i've read that several times
>>>> i don't see anything that tells me the details of how apt is performing the search
>>>
>>> I don't understand what you're asking.
>>>
>>> ~e means the rest of it is a regex (regular expression) which is matched
>>> against the source package name. (It would be nice if it specified
>>> which flavor of regex it's using, because there are many.)
>>>
>>> ^science is a regex that matches any string/line beginning with the
>>> substring "science". (At least in BRE, ERE and PCRE flavors.)
>>>
>>> So, putting it together, it should match all packages whose source package
>>> name begins with "science".
>>>
>>> When I run it on my system, I get the following result:
>>>
>>> hobbit:~$ apt list '~e^science'
>>> ESC[32mlibjs-sciencejsESC[0m/stable,stable 1.9.3+dfsg-4 all
>>>
>>> This package is not installed, so it seems it's looking at available
>>> packages. This is the package it's referring to:
>>>
>>> hobbit:~$ apt-cache show libjs-sciencejs
>>> Package: libjs-sciencejs
>>> Source: science.js
>>> Version: 1.9.3+dfsg-4
>>> [...]
>>>
>>> As you can see, its source package name is "science.js" which does in
>>> fact begin with "science". So, it looks like it's working as documented.
>>
>> apt list ~e^science is an example
>> not what i'm interested in
>> i'm interested in the details of how apt go about doing whatever it's doing
>
> Well, what details are you interested in getting?
>
> Do you want to know what files, or other data sources, it looks at? What
> parts of those files it matches against? What methods it uses to search
> through them? How it determines what does and does not count as a match?
> Something else? (Multiple somethings else?)
>
> For some of those, the answers can be found within the information
> you've already been given; for example, the "how it determines what does
> and does not count as a match" is answered by "regex", which is to say
> "regular expression". Regular expressions are a topic all on their own,
> which is amply documented in many places, one of which you've been
> pointed to elsewhere in this thread.
>
> For most of the rest of the things I suggested as ideas of what might be
> the details you're interested in getting, the only way you're going to
> find the answers is to look at the source code of apt. apt itself does
> not appear (at least not at a simple skim) to include debug or verbose
> output options, certainly not ones so extensive as to let you follow
> along step-by-step with what it's doing.
>
> In theory you could alternately (or also) run the program under strace
> or possibly a debugger, and use that to look at what functions it's
> calling and with what arguments and so forth, and use that to help
> inform your understanding of what's being done when the program runs.
> But there is only so much utility to be found in doing that without also
> referencing the source code, so you'd probably be better off going
> straight for that option instead.
>
> The source code for apt can be obtained by, among other methods, running
> 'apt source apt'; this is documented in the man page for apt-get, which
> is pointed to by the man page for apt. That works the same way with any
> package name; you can e.g. run 'apt source dpkg' or 'apt source
> xserver-xorg-core' or 'apt source xorg-server', and each of those will
> download and set up a source-package directory for the specified package.
>
> (The latter two, if I'm not mistaken, will in fact fetch and set up the
> exact same source-package directory; the first of them specifies the
> name of a binary package, and the latter the name of the source package
> from which that binary package was built.)
>
> If none of that helps you find out how to find out what you're wanting
> to know, then I'm afraid you're going to have to figure out some way to
> be more clear about exactly what it is that you're wanting to know,
> because the way you've been explaining it so far isn't conveying enough
> information for us to be able to figure out what sort of answer would
> satisfy your interest.
>
i guess that about covers it
from what i've read apt does not provide debug that let you look under the covers
it's read the code or nothing
thanks
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