I have successfully installed some packages using the command:
sudo apt-get install packagename
when I have known in advance that those packages are available. But how can I search for or get a list of what is available in the repositories?
I have successfully installed some packages using the command:
sudo apt-get install packagename
when I have known in advance that those packages are available. But how can I search for or get a list of what is available in the repositories?
From the command-line, use:
apt-cache search keyword
where the search keyword can be all or part of a package name or any words used in its description.
For example, apt-cache search proxy includes both these packages:
tinyproxy - A lightweight, non-caching, optionally anonymizing HTTP proxy tircd - ircd proxy to the twitter API
Note: the list may be long, so you can pipe the output to
lessto make it scrollable one line or one screen at a time, i.e.apt-cache search something | less.
apt-cache search .
Synaptic is often a more convenient way to do this, but requires at least an X server on your end (unless you're running a desktop environment). Install with sudo apt-get install synaptic if necessary.
Synaptic on ssh'd server via X forwarding:

Synaptic running locally on Ubuntu Desktop:

Using aptitude, apt-cache, and apt all format the output differently. (None of these require the use of sudo when searching for a package.) I prefer using apt for its readability. It highlights the package name and puts a space between the different packages. It also has [installed] listed next to each package that is already installed. Usage:
apt search keyword
The apt-cache command line tool is used for searching apt's software package cache. In simple words, this tool is used to search software packages, collect information about packages and also search for what packages are available and ready for installation on Debian- or Ubuntu-based systems.
To find a package's name along with its description before installing, use the search flag. Using search with apt-cache will display a list of matched packages with a short description.
The general syntax of apt-cache search is:
apt-cache search SearchTerm
where SearchTerm is the term you wish to search for. For example, let’s say you would like to find the description of the vsftpd package. The command you would use would be:
apt-cache search vsftpd
The possible output would be:
vsftpd - lightweight, efficient FTP server written for security
ccze - A robust, modular log coloriser
ftpd - File Transfer Protocol (FTP) server
yasat - simple stupid audit tool
To find and list down all the packages starting with vsftpd, you
could use the following command.
apt-cache pkgnames vsftpd
You may also want to run the results through more or even grep commands. For instance:
apt-cache search firefox | grep plugin
Unfortunately I don't have enough rep to add this a comment on the main answer.
But I was trying to find g++- - alike packages with apt-cache search. It's important to know in this case that keyword is a regular expression so apt-cache search g++- will not have helpful results.
apt-cache search "g[+][+][-]" would be the way to go
apt list <package> is how I recommend searching for packages. If you don't get any matches or if you're not sure what the package is named, try wrapping the argument in asterisks to get more results. For instance apt list *chrome* will yield the following:
Listing...
chrome-gnome-shell/focal,focal,now 10.1-5 all
chromium-chromedriver/focal-updates 1:85.0.4183.83-0ubuntu0.20.04.2 amd64
chromium-lwn4chrome/focal,focal 1.0-3 all
google-chrome-beta/stable 99.0.4844.17-1 amd64
google-chrome-stable/stable,now 98.0.4758.80-1 amd64
google-chrome-unstable/stable 100.0.4867.0-1 amd64
mkchromecast-alsa/focal,focal 0.3.8.1-1 all
mkchromecast-gstreamer/focal,focal 0.3.8.1-1 all
mkchromecast-pulseaudio/focal,focal 0.3.8.1-1 all
mkchromecast/focal,focal 0.3.8.1-1 all
node-chrome-trace-event/focal,focal 1.0.2-1 all
openchrome-tool/focal 1:0.6.0-3build1 amd64
python3-pychromecast/focal,focal 4.1.0-1 all
ruby-chromedriver-helper/focal,focal 2.1.0-7 all
xserver-xorg-video-openchrome-hwe-18.04/focal 3:14.5 amd64
xserver-xorg-video-openchrome/focal 1:0.6.0-3build1 amd64
Alternatively, if you'd like a description of each package, run apt search --names-only <package>. Make sure to include --names-only for more accurate results.
first I recommend you update the package index files so the list of all files in the repository you are about to create is up to date
sudo apt-get update
then use "search regex" function in apt-cache where "regex" stands for Regular Expression and is the pattern given to search. For more info about search patterns you can look up manual regex(7) by command man 7 regex or in English. A regex variable equal to . will suffice.
apt-cache search .
The above will give you ALL the results but it is not in any order that is particularly helpful for browsing.
So finally we can sort by dictionary order usingsort -d and show only a page at a time usingless.
apt-cache search . |sort -d |less
The OP aimed only to apt, which was already answered (apt search). Some people might end up here searching for solutions for other (more modern) alternatives.
Nowadays we have other sources for apps: pip, brew, flatpak and npm, to name a few popular ones. All of them also works with search subcommand.
You could handle all of the above and others with meta-package-manager, which solves XKCD #1654 (don't look #927).
apt-file search part_of_package_name
"Extended variant" is useful in case of excessive number of results:
apt-file search part_of_package_name | grep another_part_of_name
Example of searching for ssh server package if I do not know the name is ssh-server or sshserver or server-ssh etc.:
apt-file search ssh | grep server
Steps to prepare apt-file search for searching. It should be done before first usage:
sudo apt-get install apt-file
sudo apt-file update