AWS AMI instance memory static to Cloudwatch

mem_watch.sh

#!/bin/bash

export AWS_CLOUDWATCH_HOME=/opt/aws/apitools/mon # cloudwatch command line tools
export AWS_CLOUDWATCH_URL=https://monitoring.amazonaws.com # cloudwatch end point
export PATH=$AWS_CLOUDWATCH_HOME/bin:$PATH 
export JAVA_HOME=/usr/lib/jvm/jre

# cloudwatch credential
CLOUDWATCHCREDENTIAL=/root/aws-custom-monitor/cloudwatch_credential.txt

# set the region
REGION="ap-southeast-1"

# set the namespace
NAMESPACE="System/API"

# get ec2 instance id
INSTANCEID=`wget -q -O - http://169.254.169.254/latest/meta-data/instance-id`

MEMTOTAL=`free -m | grep 'Mem' | tr -s ' ' | cut -d ' ' -f 2`
MEMFREE=`free -m | grep 'buffers/cache' | tr -s ' ' | cut -d ' ' -f 4`
let "MEMUSED=100-MEMFREE*100/MEMTOTAL"
 
mon-put-data --metric-name "FreeMemoryMBytes" --namespace "$NAMESPACE" --dimensions "InstanceId=$INSTANCEID" --value "$MEMFREE" --unit "Megabytes" --aws-credential-file "$CLOUDWATCHCREDENTIAL" --region "$REGION"
 
mon-put-data --metric-name "UsedMemoryPercent" --namespace "$NAMESPACE" --dimensions "InstanceId=$INSTANCEID" --value "$MEMUSED" --unit "Percent" --aws-credential-file "$CLOUDWATCHCREDENTIAL" --region "$REGION"

exit 0