Limit an existing process with PID 1234 to only use 25% of the CPU

A tool to throttle the CPU usage of other processes.
More information: <http://cpulimit.sourceforge.net/>.
Trick copyright: tl;dr; <https://github.com/tldr-pages/tldr>

cpulimit --pid {{1234}} --limit {{25%}}

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