How to Check Package Is Installed or Not

• As a System Admin, I’ve to check some Package is installed or not.
• In this article I’ll show you how to properly check some package is installed on your system or not.

Install htop Package

[mitesh@Matrix ~]$ apt-get install htop
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following NEW packages will be installed:
  htop
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 68.0 kB of archives.
After this operation, 188 kB of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu/ trusty/universe htop amd64 1.0.2-3 [68.0 kB]
Fetched 68.0 kB in 0s (98.6 kB/s)
Selecting previously unselected package htop.
(Reading database ... 86712 files and directories currently installed.)
Preparing to unpack .../htop_1.0.2-3_amd64.deb ...
Unpacking htop (1.0.2-3) ...
Processing triggers for mime-support (3.54ubuntu1.1) ...
Processing triggers for man-db (2.6.7.1-1ubuntu1) ...
Setting up htop (1.0.2-3) ...

Remove htop Package

• After install the htop package, sometimes we don’t like installed package
• Let’s remove the htop package

[mitesh@Matrix ~]$ apt-get remove htop
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be REMOVED:
  htop
0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded.
After this operation, 188 kB disk space will be freed.
Do you want to continue? [Y/n] y
(Reading database ... 86722 files and directories currently installed.)
Removing htop (1.0.2-3) ...
Processing triggers for man-db (2.6.7.1-1ubuntu1) ...
Processing triggers for mime-support (3.54ubuntu1.1) ...

Check Package Is Installed or Not

• Most of SystemAdmin (Including Me), First try following commands

[mitesh@Matrix ~]$ dpkg -l | grep htop
rc  htop                             1.0.2-3                          amd64        interactive processes viewer
[mitesh@Matrix ~]$ echo $?
0

NOTE!: The problem with dpkg -l command is its return 0 even if package is removed from the system.

• Let’s fix the dpkg -l command to get only installed package.

Method 1

[mitesh@Matrix ~]$ dpkg --get-selections | grep -v deinstall | grep htop
[mitesh@Matrix ~]$ echo $?
1

Method 2

[mitesh@Matrix ~]$ apt-cache policy htop | grep Installed | grep -v none
[mitesh@Matrix ~]$ echo $?
1

NOTE!: As above commands return 0 only if that package is installed on your system.