Improvements to apt-file since stretch

The list of changes for apt-file in buster is rather short, but I would still like to mention a few of them in this post.

New list-indices command:

In stretch, apt-file migrated to use apt’s new acquire system and that meant a lot of changes to apt-file’s interface.  Among other, you could no longer search for source packages via the “-a source” but had to use “-Idsc” instead.  While the manpage has some runes about these names, but not everyone finds them helpful.

To do a bit better, we have included a new list-indices command in apt-file that enables you see exactly which indices that apt-file recognises and whether we can find any data in them.  This looks like the following:

$ apt-file list-indices
+-----------------+-----------------------------+-----------------+
| Index Name (-I) | DefaultEnabled (Apt config) | Index Status    |
+-----------------+-----------------------------+-----------------+
| deb             | <unset>                     | Ok              |
| udeb            | false                       | Empty (code: 4) |
| dsc             | false                       | Empty (code: 4) |
+-----------------+-----------------------------+-----------------+

At the moment, the command outputs three columns:

  • “Index Name (-I)” – This is the value you pass to -I/–index-names to search in that index.
  • “DefaultEnabled (Apt config)” – This is the value apt-file found while asking apt-config about the index configuration.  As you can disable fetching of Contents files on a “per sources.list” basis, so the above is only the default for URIs you fetch from.
  • “Index Status” – This tells you whether apt-file can actually search for anything in that index.  It comes in 3 basic status: Ok (i.e. some searchable data found), Empty (no Contents files found) and Error (an unexpected error happened while checking the status but it did not stop apt-file from generating the table).

Note: It is intended to be human-readable and is not (intended to be) machine readable.  If you need this data in a script or for automation purposes, please use apt-config plus apt-get indextargets directly and extra the data you want via those tools.  The output format of this command may change without notice (if another format is found better suited, etc.).

Status feedback (terminal-only):

The new version of apt-file also provides some feedback to your terminal while you wait for your search.  It comes in the form of a single line showing you what apt-file is doing. Below is the output from apt-file (being interrupted) at various stages.

$ apt-file show lintian
Searching for contents of the packages ...^C
$ apt-file show lintian
Searching, found 370 results so far ...^C

(note: The number of “results” here is prior to de-duplicating the results.  You may see a much larger number here than in the final result)

The output is disabled when you redirect stdout, so most scripts are unaffected by this change:

$ apt-file show lintian | head -n1
lintian: /etc/lintianrc

Faster by default:

Historically, Contents files had a human-readable header that described what the files contented, how to read the file and column headers.  Unfortunately, they made apt-file’s life harder as we had to reliably ignore these headers without losing actual data from them.  However, both dak and reprepro has stopped adding the headers, so apt-file can now skip the header filtering by default.

If you still need to search for files in Contents files with the headers, you can re-enable the check (with related performance hit) by setting apt-file::Parser::Check-For-Description-Header to true in your configuration.  E.g.

$ time apt-file search nothing-else-matches
                                          
real    0m1.853s
[...]
$ time apt-file search -o apt-file::Parser::Check-For-Description-Header=true nothing-else-matches
                                          
real    0m7.875s

Actual performance benefit largely depends on cache size and (apparently) also what you search for.  🙂

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