check-linux-uptime

#!/bin/bash
# Checks uptime
# Requires a platform supporting /proc/uptime and date tool

# Exit codes
OK=0
WARNING=1
CRITICAL=2
UNKNOWN=3

exitcode=$UNKNOWN
codetext=("Ok" "Warning" "Critical" "Unknown")

# Usage help
usage() {

  text="
USAGE: ${0} -c <seconds> -w <seconds>

-c: return CRITICAL if uptime is shorter than the value 
-w: return WARNING if uptime is shorter than the value
"
  echo "$text"

  exit $exitcode
}

# check for command line arguments
while getopts "w:c:h" option
do
  case "$option" in
    c) critical=$OPTARG;;
    w) warning=$OPTARG;;
    h) usage;;
    *) usage;;
  esac
done

[[ ! -f "/proc/uptime" ]] && echo "/proc/uptime does not exist." && exit $exitcode

# Extract the first value and strip off decimal part
uptime=$(cat /proc/uptime | cut -d' ' -f1)
uptime=${uptime%.*}

exitcode=$OK

# date magic
message=$(echo $(($uptime/86400))" days" $(date -d "1970-01-01 + $uptime seconds" "+%H hours %M minutes %S seconds"))

# threshold checks
[[ (! -z $warning) && ($uptime -lt $warning) ]] && exitcode=$WARNING
[[ (! -z $critical) && ($uptime -lt $critical) ]] && exitcode=$CRITICAL

echo "Uptime ${codetext[$exitcode]} - $message"
exit $exitcode