Perkify - APT

Written by Rich Morin.

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Path:  AreasContentHowTos

Precis:  introduction to APT usage on Perkify

Most of Perkify’s added packages are installed using Debian’s Advanced Package Toolkit (APT). So, we can use APT and related tooling to find out what we have.

Commands

While we’re trying out commands, let’s have some fun with Unix command pipelines and shell magic! You can probably guess what many of these commands and options do, but you can also use man head (etc) to find out the gritty details on any unfamilar commands. See Perkify - Manual for a brief introduction.

Investigation

In Unix-based systems, most commands are simply “executable files”. Although you’ll seldom need to investigate commands, it’s nice to know that you can. Some commands (called “scripts”) are available for inspection. For example, let’s investigate the apt_summ command (discussed below). First, where is it located in the file system?

vagrant@vagrant:~$ which apt_summ
/home/vagrant/bin/apt_summ

Next, what kind of file is it?

vagrant@vagrant:~$ file /home/vagrant/bin/apt_summ
/home/vagrant/bin/apt_summ: Ruby script, ASCII text executable

OK, it’s an ASCII text file (specifically, a Ruby script). Feel free to check it out and figure out how it works. That said, before trying to display the contents of any command, make sure that it’s a text file. Sending anything else to the terminal will print a lot of trash and seriously confuse your SSH session. Don’t go there…

apt_summ

Perkify’s apt_summ command generates a one-line summary for each installed package. The first part of each line is Debian’s name for the package. Then, in parentheses, comes the package’s “version” string. This can help you to determine whether your version is up to date. Finally, there is a terse description of the package.

Note: While building the Perkify “box”, we run apt_summ a few times. The results are available in ~/_base/data; see ~/_base/make/add_ons for the relevant code.

Given that this list is about 2500 lines long (and counting…), you’ll usually want to filter it in some manner. Let’s generate the list and then display only the first line:

vagrant@perkify:~$ apt_summ | head -1
a2ps (1:4.14-4) - GNU a2ps - 'Anything to PostScript' converter ...

That worked nicely; let’s number the lines and then display the last one:

vagrant@perkify:~$ apt_summ | cat -n | tail -1
2439  zlib1g-dev:amd64 ...

Now, let’s display a couple of lines that contain “PostScript”, ignoring case distictions:

vagrant@perkify:~$ apt_summ | grep -i postscript | head -2
a2ps (...) - GNU a2ps - 'Anything to PostScript' converter ...
evince (...) - Document (PostScript, PDF) viewer

apropos

Often, the package name will match at least one of the commands it provides. So, you may have luck finding a man page with apropos(1):

vagrant@perkify:~$ apropos a2ps | head
a2ps (1)             - format files for printing on a PostScript printer
a2ps-lpr-wrapper (1) - lp/lpr wrapper script for GNU a2ps on Debian
texi2dvi4a2ps (1)    - Compile Texinfo and LaTeX files to DVI or PDF

Then, of course, you can check out any man pages that seem promising:

vagrant@perkify:~$ man a2ps
...

apt search

You can also ask APT to help you find packages. For example, apt search performs a keyword-based search of available packages. The output can be voluminous, so you may want to store it in a file or pipe it through a filter (e.g., head(1), less(1)):

vagrant@perkify:~$ apt search a2ps | head
Sorting... Done
Full Text Search... Done
a2ps/disco,now 1:4.14-4 amd64 [installed]
  GNU a2ps - 'Anything to PostScript' converter and pretty-printer
...

apt-cache show a2ps

If you know the name of the package, you can ask APT for detailed information.

vagrant@perkify:~$ apt-cache show a2ps
Package: a2ps
Architecture: amd64
Version: 1:4.14-4
Priority: optional
Section: universe/text
...

Web Sites

There are several useful web sites you can visit to find out about packages. Our current release is based on Ubuntu “Eoan Ermine” (19.10) and the apt(1) command automagically uses the appropriate archive sites. However, to get information on a specific package from a web site, you’ll have to include the current base release (e.g., “eoan”) in the URL:

To be continued…