#!/bin/bash
###
#
# Verify the debian release.
#
# @AUTHOR: Patrik Dufresne (http://patrikdufresne.com)
# Copyright 2015 Patrik Dufresne
# Last modified 2015-10-30
# Please send all comments, suggestions, bugs and patches to (info AT patrikdufresne DOT com)
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, version 2 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
###

VERSION=1.0
AUTHOR="Patrik Dufresne"
SERVICE="DEBIAN"

# Replacement for the exit function, will cleanup any tempfiles or such
# before exiting.
function cleanup {
    exit $1
}

declare -rx PROGNAME=${0##*/}
declare -rx PROGPATH=${0%/*}/

if [ -r "${PROGPATH}utils.sh" ] ; then
    source "${PROGPATH}utils.sh"
else
    echo "Can't find utils.sh. This plugin needs to be run from the same directory as utils.sh which is most likely something like /usr/lib/nagios/plugins or /usr/lib64/nagios/plugins"
    printf "Currently being run from %s\n" "$PROGPATH"
    # Since we couldn't define STATE_UNKNOWN since reading utils.sh
    # failed, we use 3 here but everywhere else after this use cleanup $STATE
    cleanup 3
fi

# Set STATE to UNKNOWN as soon as we can (right after reading in util.sh
# where the STATES are defined)
STATE=$STATE_UNKNOWN

# make sure that any external commands are installed, in the PATH and
# executable. The following example is stupid because of course date is
# installed but it's the only command this trivial check really uses
BC=/usr/bin/bc
if [ ! -x "$BC" ] ; then
    echo "$BC utility is not installed, in your path and executable. Exiting."
    cleanup $STATE_UNKNOWN
fi

# provide a quick one liner of how to use the program
function usage {
    printf " %s %s for Nagios - Usage %s \
-w <warning threshold> -c <critical threshold> \
[-t timeout] [-v [-v [-v]]]\n" "$PROGNAME" "$VERSION" "$PROGNAME"
    cleanup $STATE_UNKNOWN
}

# provide detailed explanations of the command line syntax
function longhelp {
    # put your long help here
    printf "%s plugin version %s for Nagios by %s
  -h, --help          Display this message.
  -w, --warning=val   Set the debian release version warning threshold.
  -c, --critical=val  Set the debian release critical threshold.
  -t, --timeout=sec   Set script timeout in seconds.
  -v, --verbose       Up the verbosity level by one.
  --verbosity=val     Set the verbosity level to val.
  -V, --version       Print version information.
  --range_help        Explain threshold ranges.
" "$PROGNAME" "$VERSION" "$AUTHOR"
    cleanup $STATE_UNKNOWN
}

# explanatory function you probably want to keep
function range_help {
    printf "
The format for ranges in Nagios can be confusing and it isn't always followed.

[@]start[:[end]]

Here are some example ranges:

Range   |  Generate an alert if value is    |  In English
--------+-----------------------------------+---------------------------------
10      |  outside the range of {0 .. 10}   |  Greater than 10
@10     |  inside the range of {0 .. 10}    |  Less than or equal to 10
10:     |  outside {10 .. ∞}                |  Greater than 10
~:10    |  outside the range of {-∞ .. 10}  |  Less than 10 including negative
10:20   |  outside the range of {10 .. 20}  |  Between 10 and 20
@10:20  |  inside the range of {10 .. 20}   |  Anything from 10 to 20
10      |  outside the range of {0 .. 10}   |  Greater than 10 or less than 0

Formal Rules:
1. start ≤ end
2. start and ":" is not required if start=0
3. if range is of format \"start:\" and end is not specified, end is infinity
4. to specify negative infinity, use "~"
5. alert is raised if metric is outside start and end range (inclusive)
6. if range starts with "@", then alert if inside this range (inclusive)
    10      < 0 or > 10, (outside the range of {0 .. 10})
    10:     < 10, (outside {10 .. ∞})
    ~:10    > 10, (outside the range of {-∞ .. 10})
    10:20   < 10 or > 20, (outside the range of {10 .. 20})
    @10:20  ≥ 10 and ≤ 20, (inside the range of {10 .. 20})
    10      < 0 or > 10, (outside the range of {0 .. 10})

More help at http://nagiosplug.sourceforge.net/developer-guidelines.html
"
    cleanup $STATE_UNKNOWN
}

# use getopt, trust me on this one. It's the easiest way
getopt -T
if [ $? -ne 4 ] ; then
    printf "%s: getopt is in compatibility mode.\n" "$SCRIPT"
    cleanup $STATE_UNKNOWN
fi

# Tell it which switches and longswitches you'll take and place a trailing
# colon (:) on the ones take arguments. Nagios guidelines require you to
# use all the ones specified below with the exception of --verbosity which I've
# added to circumvent the awkward -v -v -v syntax. Getopt takes care of
# positional parameters and errors for missing expected arguments so we can
# shift later without checking
RESULT=`getopt --name "$SCRIPT" --options "-h,-V,-v,-c:,-w:,-t:" --longoptions "help,version,verbose,verbosity:,warning:,critical:,timeout:" -- "$@"`

# make the result of getopt your new argument list ($@)
eval set -- "$RESULT"

declare WARNING
declare CRITICAL
# all scripts should have a mechanism to terminate themselves if they are
# running for too long. Scripts you might think of as innocuous could end
# up waiting forever on I/O, especially if a disk is failing
declare -i TIMELIMIT=15
# Nagios defines behavior for VERBOSITY 0 (default) through 3
declare -i VERBOSITY=0

while [ $# -gt 0 ] ; do
    case "$1" in
        -h | --help)
            longhelp;;
        -V | --version)
            print_revision "$PROGNAME" "$VERSION"
            cleanup $STATE;;
        -v | --verbose)
            VERBOSITY=$(($VERBOSITY + 1));;
        --verbosity)
            shift
            VERBOSITY=$1;;
        -w | --warning)
            shift
            WARNING=$1;;
        -c | --critical)
            shift
            CRITICAL=$1;;
        -t | --timeout)
            shift
            TIMELIMIT=$1;;
        --)
            shift
            break;;
        *)
            echo "Option $1 not supported. Ignored." >&2;;
    esac
    shift
done

#Verbosity level    Type of output
#0            Single line, minimal output. Summary
#1            Single line, additional information (eg list processes that fail)
#2            Multi line, configuration debug output (eg ps command used)
#3            Lots of detail for plugin problem diagnosis
if [ $VERBOSITY -gt 3 ] ; then
    shopt -o -s xtrace
fi

# Check that the thresholds provided are valid strings
if [ -z "$WARNING" -o -z "$CRITICAL" ] ; then
    range_help
else
    # positive values only
    WARNFORMAT=`echo "$WARNING" | grep -c '^@\?\([0-9]\+:[0-9]*\|[0-9]\+\)$'`
    CRITFORMAT=`echo "$CRITICAL" | grep -c '^@\?\([0-9]\+:[0-9]*\|[0-9]\+\)$'`
    OK=$(( $WARNFORMAT + $CRITFORMAT ))
    if [ $OK -lt 2 ] ; then
        echo "Please check the format of your warning and critical thresholds."
        range_help
    fi
fi

# what needs to happen in the event of a timeout
function timeout {
    echo "UNKNOWN - script timed out after $TIMELIMIT seconds."
    cleanup $STATE_UNKNOWN
}

# since we've processed the options which potentially set the timeout limit,
# we can setup a timeout trap now
trap timeout USR1
    ( sleep $TIMELIMIT; if [ `pgrep -U $USER -f "$SCRIPT" | grep -c ^$$$` -gt 0 ] ; then kill -USR1 $$ ; fi; ) </dev/null &>/dev/null &

    VALUE=$(cat /etc/debian_version)

trap - USR1

function check_value {
    # If the range starts with an @, alert if value is inside the range,
    # otherwise alert if value is outside of range.
    INSIDE=`echo "$1" | grep -c '^@'`
    RANGE=`echo "$1" | sed 's/^@//'`

    # Start is anything left of the colon or 0.
    # End is anything right of the colon or the whole string if there's no
    # colon or infinity if there is a colon and nothing to the right of it

    # is there a colon?
    PARTS=`echo "$RANGE" | awk -F : '{ print NF }'`
    if [ $PARTS -gt 1 ] ; then
        START=${RANGE%%:*}
        END=${RANGE##*:}
    else
        START=0
        END=$RANGE
    fi

    # 4. to specify negative infinity, use "~"
    if [ "$START" == "~" ] ; then
        START=-999999999
    fi

    if [ -z "$END" ] ; then
        END=999999999
    fi

    if [ $START -gt $END ] ; then
        echo "In threshold START:END, START must be less than or equal to END"
        range_help
    fi

    # if the range starts with an @, alert if value is inside the range, otherwise alert if value is outside of range
    # all ranges are inclusive of endpoints so we use less than or equal on the inside and just less than on the outside
    if [ "$INSIDE" -gt 0 ] ; then
        if [ $(echo "$START <= $2 && $2 <= $END" | bc) -eq 1 ] ; then
          return 1
        fi
    elif [ $(echo "$2 < $START || $END < $2" | bc) -eq 1 ] ; then
        return 1
    fi

    return 0
}

# check conditions - yes this is ugly, blame BASH. If you want to blame me, please provide a cleaner way that is as fast or faster
check_value "$CRITICAL" "$VALUE"
if [ $? -gt 0 ] ; then
	STATE=$STATE_CRITICAL
else
	check_value "$WARNING" "$VALUE"
	if [ $? -gt 0 ] ; then
		STATE=$STATE_WARNING
	else
		STATE=$STATE_OK
	fi
fi

# STATE - Message | 'label'=value[unit of measure];[warn];[crit];[min];[max]
OUT="v$VALUE ($(uname -m -r))"

case $STATE in
    $STATE_OK)
        printf "%s OK: %s\n" "$SERVICE" "$OUT $PERF";;
    $STATE_WARNING)
        printf "%s WARNING: %s\n" "$SERVICE" "$OUT $PERF";;
    $STATE_CRITICAL)
        printf "%s CRITICAL: %s\n" "$SERVICE" "$OUT $PERF";;
    $STATE_UNKNOWN)
        printf "%s UNKNOWN: %s\n" "$SERVICE" "$OUT $PERF";;
esac

cleanup $STATE