Finding package versions in apt

chapters/ch04-system.tex

@@ -4,13 +4,90 @@
 
 \lettrine{S}{ometimes} you add something to your \texttt{.bashrc} file (such as a new bash alias)\index[concepts]{bash alias} and you need to reload it. Of course, this file is reloaded every time you log in, but you may not wish to log out and then log back in if you are in the middle of important work. There are few different ways to do this:
 
-\begin{Verbatim}[]
+\begin{Verbatim}[frame=single, breaklines=true]
 source ~/.bashrc
 \end{Verbatim}
 \index{source}
 
 and of course a shorter way:
 
-\begin{Verbatim}[]
+\begin{Verbatim}[frame=single, breaklines=true]
 . ~/.bashrc
-\end{Verbatim}
+\end{Verbatim}
+
+\section{To See if a Package Exists in the \texttt{apt} Repository}
+
+\lettrine{W}{hile} there are many ways to install software on a Linux system, the easiest way is usually through the package manager, which on Ubuntu is \texttt{apt}. \index{apt} To see if a package is available in that repo, we can use 
+
+\begin{Verbatim}[frame=single, breaklines=true]
+apt-cache search <package>
+\end{Verbatim}
+
+As an example, searching for the Okular document viewer in \texttt{apt} returns the following:
+
+\begin{Verbatim}[]
+libokular5core9 - libraries for the Okular document viewer
+okular - universal document viewer
+okular-backend-odp - Okular backend for ODP documents
+okular-backend-odt - Okular backend for ODT documents
+okular-dev - development files for the Okular libraries
+okular-extra-backends - additional document format support for Okular
+okular-mobile - mobile support for Okular
+qml-module-org-kde-okular - mobile support for Okular - QML modules
+\end{Verbatim}
+
+This does not tell us which version is available however. We have a couple of options here. First, we can use 
+
+\begin{Verbatim}[frame=single, breaklines=true]
+apt policy <package>
+\end{Verbatim}
+
+Using that for Okular returns the following:
+
+\begin{Verbatim}[breaklines=true]
+okular:
+  Installed: (none)
+  Candidate: 4:21.12.3-0ubuntu1
+  Version table:
+     4:21.12.3-0ubuntu1 500
+        500 http://us.archive.ubuntu.com/ubuntu jammy/universe amd64 Packages
+        100 /var/lib/dpkg/status
+\end{Verbatim}
+
+We can also use:
+
+\begin{Verbatim}[frame=single, breaklines=true]
+apt search <package>
+\end{Verbatim}
+
+Which gives a more detailed listing with the available version of all related packages:
+
+\begin{Verbatim}[]
+Sorting... Done
+Full Text Search... Done
+libokular5core9/jammy 4:21.12.3-0ubuntu1 amd64
+  libraries for the Okular document viewer
+
+okular/jammy,now 4:21.12.3-0ubuntu1 amd64 [residual-config]
+  universal document viewer
+
+okular-backend-odp/jammy 1:3.2.1+dfsg-5 amd64
+  Okular backend for ODP documents
+
+okular-backend-odt/jammy 1:3.2.1+dfsg-5 amd64
+  Okular backend for ODT documents
+
+okular-dev/jammy 4:21.12.3-0ubuntu1 amd64
+  development files for the Okular libraries
+
+okular-extra-backends/jammy 4:21.12.3-0ubuntu1 amd64
+  additional document format support for Okular
+
+okular-mobile/jammy 4:21.12.3-0ubuntu1 amd64
+  mobile support for Okular
+
+qml-module-org-kde-okular/jammy 4:21.12.3-0ubuntu1 amd64
+  mobile support for Okular - QML modules
+\end{Verbatim}
+
+\ktcbox{I generally prefer to install software from the \texttt{apt} repository, but sometimes it does not have the most recent version. These tools allow me to quickly check which version the repo does have. If the version is acceptable, I can install from there, or if not, I can explore other options.}