join(1) on Linux
The text caf9bf8ed6e4, as Debian 11 (Bullseye) shipped it.
join lines of two files on a common field
Flags it lists
-
--check-order -
--header -
--help -
--ignore-case -
--nocheck-order -
--version -
--zero-terminated -
-1 -
-2 -
-a -
-e -
-i -
-j -
-o -
-t -
-v -
-z