Sometimes I need to check the installed package version, compare it with the available version, or verify that the correct version is already installed. I will show you how to quickly perform these checks.

Check the version of the installed package

You can quickly check the version of the installed package using dpkg command.

$ dpkg -s cpp
Package: cpp
Status: install ok installed
Priority: optional
Section: interpreters
Installed-Size: 63
Maintainer: Debian GCC Maintainers <debian-gcc@lists.debian.org>
Architecture: amd64
Multi-Arch: allowed
Source: gcc-defaults (1.120)
Version: 4:4.7.2-1
Depends: cpp-4.7 (>= 4.7.2-1~)
Suggests: cpp-doc
Conflicts: cpp-doc (<< 1:2.95.3)
Description: GNU C preprocessor (cpp)
 The GNU C preprocessor is a macro processor that is used automatically
 by the GNU C compiler to transform programs before actual compilation.
 .
 This package has been separated from gcc for the benefit of those who
 require the preprocessor but not the compiler.
 .
 This is a dependency package providing the default GNU C preprocessor.

Print the most important information in the table.

$ dpkg -l cpp
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name               Version      Architecture     Description
+++-==================-============-================-===========================
ii  cpp                4:4.7.2-1    amd64            GNU C preprocessor (cpp)

A more efficient solution would be to filter package version using grep command.

$ dpkg -s cpp | grep Version
Version: 4:4.7.2-1

Use dpkg-query utility to output data using a custom format.

$ dpkg-query -W --showformat='${Package} version ${Version} for architecture ${Architecture}\n' cpp
cpp version 4:4.7.2-1 for architecture amd64

You will receive an error if the given package is not installed.

$ dpkg -s mc
dpkg-query: package 'mc' is not installed and no information is available
Use dpkg --info (= dpkg-deb --info) to examine archive files,
and dpkg --contents (= dpkg-deb --contents) to list their contents.

Check the version of the installed or available package

You should use utilities described in this section instead of the previous one if you are not sure that the package is already installed.

apt-cache

Use this command to query APT cache and list current and available package versions.

$ apt-cache policy iceweasel
iceweasel:
  Installed: 31.2.0esr-2~deb7u1
  Candidate: 31.2.0esr-2~deb7u1
  Version table:
 *** 31.2.0esr-2~deb7u1 0
      500 http://security.debian.org/ wheezy/updates/main amd64 Packages
      100 /var/lib/dpkg/status
     24.4.0esr-1~deb7u2 0
      500 http://ftp.task.gda.pl/debian/ wheezy/main amd64 Packages

aptitude

Current and available package versions can also be displayed using aptitude utility.

$ aptitude versions ^iceweasel$
Package iceweasel:
p A 24.4.0esr-1~deb7u2                        stable                 500
i A 31.2.0esr-2~deb7u1                        stable                 500

Of course, you can print data using the custom format in columns or without them.

$ aptitude search snort -F "%c %M %p %V %v"
p   fwsnort                                   1.6.2-1        <none>
i   snort                                     2.9.2.2-3      2.9.2.2-3
i A snort-common                              2.9.2.2-3      2.9.2.2-3
i A snort-common-libraries                    2.9.2.2-3      2.9.2.2-3
p   snort-doc                                 2.9.2.2-3      <none>
p   snort-mysql                               2.9.2.2-3      <none>
p   snort-pgsql                               2.9.2.2-3      <none>
v   snort-rules                               <none>         <none>
i A snort-rules-default                       2.9.2.2-3      2.9.2.2-3

Use an additional --disable-columns parameter if you want to disable columns.

Ending notes

Please read dpkg, dpkg-query, aptitude manual pages and install aptitude-doc-en package for additional information.