arguments. The external command can decide to decline the
service by exiting with a non-zero status (or to allow it by
exiting with a zero status). It can also look at the $REMOTE_ADDR
- and $REMOTE_PORT environment variables to learn about the
+ and `$REMOTE_PORT` environment variables to learn about the
requestor when making this decision.
+
The external command can optionally write a single line to its