1-liner to get latest version in a changelog file

Heres the one-liner in a code block:

cat debian/changelog | awk '{print $2;}' | sed 1q | tr -d '()' | cut -d - -f 1

This code is used to extract a piece of information (the version number of a Debian package) from a well-structured text (the Debian changelog file).

Lets explain each step and observe transformation of partial output:

1. cat debian/changelog: This command is used to view the content of the debian/changelog file.

json-toolkit (1.2.0-4) focal; urgency=medium
...

2. awk '{print $2;}': AWK is a programming language that is designed for text processing. This portion of the one-liner attempts to print out the second field (the fields are divided by whitespaces by default) of every line of debian/changelog. Characters inside the parentheses are considered one field.

(1.2.0-4)
...

3. sed 1q: SED is a stream editor. It can perform lots of functions on files like, searching, find and replace, insertion/deletion. Here, its used to quit(print and then quit) after the first line.

(1.2.0-4)

4. tr -d '()': TR is a command-line utility for translating or deleting characters. This portion of the one-liner is used to delete the parentheses.

1.2.0-4

5. cut -d - -f 1: The cut is a command-line utility for cutting sections from each line of files. This piece of code is used to cut the string into pieces by - and then print out the first piece.

1.2.0

In conclusion, this one-liner reads the debian/changelog file, and then retrieves and formats the version number of the latest package.