check_remaining_memory.bash

#!/bin/bash

set -ue

usage() {
    cat <<EOT
Usage: `basename $0` [-w|-c|-h]
    -w  warning_threshold
        set warning threshold (default 20)
    -c  critical_threshold
        set critical threshold (default 10)
    -h  print the help message and exit
EOT
}

# Exit codes
state_ok=0
state_warning=1
state_critical=2
state_unknown=3

# Defaults
warning_threshold="1024"
critical_threshold="512"

while getopts "w:c:h" opt; do
    case $opt in
        w)
            warning_threshold=$OPTARG
            ;;
        c)
            critical_threshold=$OPTARG
            ;;
        *)
            usage
            exit $state_unknown
            ;;
    esac
done

# Exit if overcommit_memory is not 2
overcommit_memory=$(cat /proc/sys/vm/overcommit_memory)
if [ $overcommit_memory -lt 2 ]; then
    info="overcommit_memory is $overcommit_memory (CommitLimit is useless)"
    echo $info
    exit $state_ok
fi

limit=$(awk '$1 ~ /CommitLimit/ {print $2}' /proc/meminfo)
committed=$(awk '$1 ~ /Committed_AS/ {print $2}' /proc/meminfo)

remain=$((limit - committed))


if [ $remain -lt $critical_threshold ]; then
    exitstatus=$state_critical
    info="(CRITICAL)"
elif [ $remain -lt $warning_threshold ]; then
    exitstatus=$state_warning
    info="(WARNING)"
else
    exitstatus=$state_ok
    info="(OK)"
fi


info="${info} remain: ${remain} (Committed: ${committed} / Limit: ${limit})"
echo $info
exit $exitstatus

sample

sh-4.1$ bash get_meminfo.sh
2678488 Committed/Limit (371540/3050028)

remain: 2678488 (Committed: 371540 / Limit: 3050028)

[hfm@sc ~]$ ./get_meminfo.sh
(CRITICAL) remain: -3471396 (Committed: 5030160 / Limit: 1558764)