Nagios plugin fails to run a command over NRPE

I have the following plugin whose status is OK on core. #!/usr/local/bin/bash if [ "$1" = "-w" ] && [ "$2" -lt "101" ] && [ "$3" = "-c" ] && [ "$4" -lt "101" ] ; then warn=$2 crit=$4 AVAILMEMPERC=$(free -m | grep mem_avail | awk '{print $7}'| tr -d %]) if [ ${AVAILMEMPERC} -gt $warn ] && [ ${AVAILMEMPERC} -gt $crit ];then echo "OK - Available Memory = $AVAILMEMPERC% | Available memory=$AVAILMEMPERC%;$warn;$crit;0;100" exit 0 elif [ ${AVAILMEMPERC} -lt $warn ] && [ ${AVAILMEMPERC} -gt $crit ]; then echo "WARNING - Available Memory = $AVAILMEMPERC% | Available memory=$AVAILMEMPERC%;$warn;$crit;0;100" exit 1 else echo "CRITICAL - Available Memory = $AVAILMEMPERC% | Available memory=$AVAILMEMPERC%;$warn;$crit;0;100" exit 2 fi else echo "$0 - Nagios Plugin for checking the available memory in a Linux system" echo "" echo "Usage: $0 -w -c " echo " = warnlevel and critlevel is warning and critical value for alerts." echo "" echo "EXAMPLE: $0 -w 10 -c 5 " echo " = This will send warning alert when available memory is less than 10%, and send critical when it is less than 5%" echo "" exit 3 fi When I run it locally on the remote machine, it runs fine. I get the right output. But on the web GUI, I see that Nagios cannot extract the variable AVAILMEMPERC value For example, if I simplify the plugin to below #!/usr/local/bin/bash warn=$2 crit=$4 AVAIL_MEM_PERCENTAGE="$(free -m)" echo "OK - ${AVAIL_MEM_PERCENTAGE}" The only output I see on GUI is OK - When I run it on command line, I do get the entire free -m output Tried the following and it doesn't write anything. I gave 777 permissions to /tmp and the files. free -m > /tmp/check_avail_memory.out Seems like a permissions issue? It runs on Nagios Core though. If I replace free with top nagios is able to write to the file. I have downloaded free from here http://people.freebsd.org/~rse/dist/freebsd-memory . As I said it runs fine on the remote machine. I have made sure the paths are correct on FreeBSD and it is executable. Couldn't find any relevant logs to this except for the plugin output.