list of installed packages without using apt?
Robert Heller
heller at deepsoft.com
Mon Nov 27 23:43:23 UTC 2017
At Mon, 27 Nov 2017 18:14:53 -0500 "Ubuntu user technical support, not for general discussions" <ubuntu-users at lists.ubuntu.com> wrote:
>
> On 2017-11-27 17:18, Stuart McGraw wrote:
> > Is there some way of getting output similar to 'apt list --installed'
> > without using apt? Specifically I want a list of installed packages,
> > their version numbers, and whether they were installed at my request
> > or as a dependency. dpkg-query provides the first two items and I
> > think apt-mark the last, but the problem is combining them.
> >
> > I dont want to use apt because: 1) I am using in a shell script and
> > apt prints an annoying warning, 2) The warning recommends against
> > using apt in scripts :-) I want to use basic low-level commands
> > and not large complex things like apt or aptitude.
>
> 1) Get rid of (most) warnings by throwing them away:
> $ command-that-generates-a-warning 2> /dev/null
> $
> The "2>" takes the secondary output stream -- "STDERR" -- and throws it
> away.
> Note, of course, that this is dangerous if there's even a medium chance
> you care about error messages from the command you're executing.
>
> 2) Apt, etc., are pretty much front-ends against files in
> /var/lib/apt/lists/ . (Anyone who knows better, please correct me --
> it's been a while since I've dug into this.) And if you really want to
> get into it, feel free to roll your own scripts against those files.
> But there simply aren't "low-level commands" that deal with those files
> -- at least, not ones without the word "apt" in them. ;-)
There is a lower level command (that does not even mess with the files in
/var/lib/apt/lists/) -- dpkg, and its friend dpkg-query. These commands can
also be useful.
And since the files in /var/lib/apt/lists/ are *text* files, they can be
dealth with using grep and various other commands, like awk or perl or python
or tcl.
>
> $.02,
>
> -Ken
>
--
Robert Heller -- 978-544-6933
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