Strange nrpe interaction


I am trying to use the plugin dowloaded from NagiosExchange ( [=947]]([p_view) )

It works perfectly when run from the command line of the monitored host, but when I try to use NRPE to check it from the Nagios server I get the following error:

NRPE: Unable to read output

My service definition:

define service{
use remote-service
host_name grdb
service_description MySQL check
check_command check_mysqld

Command definition:

‘check_mysqld’ command definition

define command{
command_name check_mysqld
command_line $USER1$/check_nrpe -H $HOSTNAME$ -c check_mysqld

and NRPE command definition on the remote machine:

command[check_mysqld]=/usr/local/nagios/libexec/ -a open-files -w 4000 -c 4500 -f

Any thoughts?