When you install Elasticsearch from Homebrew, it prints out the following message:
plugin script: /usr/local/Cellar/elasticsearch/2.2.0_1/libexec/bin/plugin
This shows for your system where the
plugin script is installed (it should be the same as mine, unless you've setup a custom location for Homebrew).
I'd also like to add that you can find the same with
$ find -L $(brew --prefix elasticsearch) -type f -name plugin
$ find $(brew --cellar elasticsearch) -type f -name plugin
from the command line (kegs are symlinked from
/usr/local/opt/, so you can get to it from either of these).
The scripts in
bin off a keg are symlinked from
/usr/local/bin which is usually included in your
plugin is too generic of a name to be included on the path. Lastly, the script will be renamed to
elasticsearch-plugin in a future version of Elasticsearch; when that happens we will revisit this.