Convert existing timestamps in a text file (eg. a log file) into [r]elative format

Add timestamps to every line from standard input.
More information: <https://joeyh.name/code/moreutils/>.
Trick copyright: tl;dr; <https://github.com/tldr-pages/tldr>

cat {{path/to/file}} | ts -r

click the source code to copy install ts on any operating system with command-not-found.com