How to install and use GNU Grep in macOS
GNU grep is not part of coreutils. To install, run

brew install grep


As with coreutils, this doesn't automatically replace the existing grep

==&gt; Caveats
All commands have been installed with the prefix "g".
If you need to use these commands with their normal names, you
can add a "gnubin" directory to your PATH from your bashrc like:
  PATH="/usr/local/opt/grep/libexec/gnubin:$PATH"


So after installing you can either use ggrep, gegrep and gfgrep; or extend PATH as shown above to use grep etc. The second option may confuse some macOS specific scripts though in case the options differ.