Probing installed packages/files efficiently using dlocate command

It is crucial to efficiently probe packages and files that are already installed on your Linux system, like

• finding the package that a particular file on your system is belonging to,
• checking filenames that are contained in an already installed package.

Recently, I have found that using dlocate command rather than dpkg possibly boosts productivity in doing so. Compared to dpkg, dlocate excels particularly in

• search speed,
• search space,
• search with integrated regular expressions.

The following examples illustrate the differences between dlocate and dpkg. The examples are based on a scenario where we probe the anthy-el package (a Japanese input system for Emacs) that contains an elisp file anthy.el as part of it.

Example 1

Using dlocate, one can search in "package_name vs file_name" space with regular expressions:

$ dlocate 'anthy\.el'
anthy-el: /usr/share/emacs/site-lisp/anthy/anthy.el

In the example, the file name anthy.el (which is owned by the anthy-el package) was matched.

Example 2

Using dlocate -l, one can search in "package_name vs package_description" space with regular expressions:

$ dlocate -l anthy
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Installed/Config-files/Unpacked/Failed-config/Half-installed
|/ Err?=(none)/Hold/Reinst-required/X=both-problems (Status,Err: uppercase=bad)
||/ Name                        Version                     Description
+++-===========================-===========================-========================================================================
ii  anthy                       9100h-0ubuntu1              input method for Japanese - backend, diction
un  anthy-cannadic                                    (no description available)
un  anthy-cannadic-2ch                                (no description available)
ii  anthy-el                    9100h-0ubuntu1              input method for Japanese - elisp frontend
ii  ibus-anthy                  1.2.0.20090813-2            anthy engine for IBus
ii  libanthy0                   9100h-0ubuntu1              input method for Japanese - runtime library
un  scim-anthy                                        (no description available)
rc  uim-anthy                   1:1.5.6-0ubuntu1            Anthy plugin for uim

Note that even not-installed packages are included in the search space which is not the case of dpkg -l.

Example 3

Using dpkg -l, one can search in "package_name" space, where only exact matches will be hit (regular expressions not available):

$ dpkg -l anthy
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Cfg-files/Unpacked/Failed-cfg/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name                             Version                          Description
+++-================================-================================-================================================================================
ii  anthy                            9100h-0ubuntu1                   input method for Japanese - backend, dictionary and utility

Example 4

Using dpkg -l | grep, one can search in "package-vs-description" space. However, this is much slower than using dlocate, and not-installed packages are excluded in the search space:

$ dpkg -l | grep anthy
ii  anthy            9100h-0ubuntu1          input method for Japanese - backend, diction
ii  anthy-el         9100h-0ubuntu1          input method for Japanese - elisp frontend
ii  ibus-anthy       1.2.0.20090813-2        anthy engine for IBus
ii  libanthy0        9100h-0ubuntu1          input method for Japanese - runtime library
rc  uim-anthy        1:1.5.6-0ubuntu1        Anthy plugin for uim

Example 5

To show file names contained in a particular package, dlocate -L and dpkg -L work similarly. However, dlocate performs much faster.

The fastest way to show all files contained in the anthy package:

$ dlocate -L anthy

An equivalent, but slower way using dpkg:

$ dpkg -L anthy

Since the default search space of dlocate is the "package_name vs package_description" space, one can achieve approximately the same result by the following naive way:

$ dlocate anthy: