[Linux] Managing Program Versions with update-alternatives

update-alternatives Command

I first came across this command when I was looking for an easy way to switch between multiple versions of PHP installed locally. The update-alternatives command is a Linux program that manages symbolic links.

Let’s look at a scenario of using update-alternatives in a situation where multiple PHP versions are installed.

Managing PHP Versions with update-alternatives Command

Checking registered symbolic links

$ sudo update-alternatives --config php
update-alternatives: error: no alternatives for php

First, check if there is any information set for PHP. Currently, it indicates that there is none.

Registering symbolic links

sudo update-alternatives --install /usr/bin/php php /usr/bin/php7.2 1
sudo update-alternatives --install /usr/bin/php php /usr/bin/php8.2 2

Let’s consider a situation where PHP 7.2 and 8.2 are installed locally, and we want to manage the default php command. The above commands add symbolic options for /usr/bin/php. php7.2 and php8.2 are the executable paths for PHP 7.2 and PHP 8.2, respectively, and the numbers 1 and 2 represent priorities.

Checking and selecting symbolic links

$ sudo update-alternatives --config php
There are 2 choices for the alternative php (providing /usr/bin/php).

  Selection    Path                      Priority   Status
------------------------------------------------------------
* 0            /usr/bin/php7.2            2         auto mode
  1            /usr/bin/php8.2            1         manual mode
  2            /usr/bin/php7.2            2         manual mode
Press <enter> to keep the current choice[*], or type selection number: 1

Running this command displays a list of available PHP versions on the system. You can input the number next to each version to choose the default PHP version. Selecting 1 changes the version when using the php -v command.

$ php -v
PHP 8.2.13 (cli) (built: Dec  9 2023 00:20:40) (NTS)
Copyright (c) The PHP Group

When multiple program versions are installed, update-alternatives allows for easy and quick management of versions. However, if the program language provides virtual environments, managing them through that method might be more effective.