Parse Nagios plugins ranges in Bash. Only integers

nagios_range.bash

#!/usr/bin/env bash

# Parse Nagios plugins ranges in Bash. Only integers.
# https://nagios-plugins.org/doc/guidelines.html#THRESHOLDFORMAT

set -euo pipefail

inrange () {
  local r v
  local v1 v2
  local outter
  local sIFS

  r="$1"
  v="$2"

  case "$r" in
    @*) outter=true; r="${r/@/}";;
    *) outter=false;;
  esac

  sIFS=$IFS

  IFS=:
  set -- $r
  v1=${1-}
  v2=${2-}
  IFS=$sIFS

  case "$v1" in
    $r) v2=$v1; v1=0;;
    ~*)  v1=;;
  esac

  if $outter; then
    { [ -n "$v1" ] && [ "$v" -le "$v1" ]; } || { [ -n "$v2" ] && [ "$v" -ge "$v2" ]; }
  else
    { [ -z "$v1" ] || [ "$v" -ge "$v1" ]; } && { [ -z "$v2" ] || [ "$v" -le "$v2" ]; }
  fi
}

test_inrange () {
  printf "%s ~~ %s\t" $2 $1
  if inrange "$1" "$2"; then
    printf 'IN '
    if $3; then
      echo '- OK'
    else
      echo '- FAILED'
    fi
  else
    printf 'OUT '
    if $3; then
      echo '- FAILED'
    else
      echo '- OK'
    fi
  fi
}

test_inrange '-123:456' 222 true
test_inrange '-456:-123' -222 true
test_inrange '123' -22 false
test_inrange '123' 1 true
test_inrange '123' 222 false
test_inrange '123:' 222 true
test_inrange '123:456' 222 true
test_inrange '123:456' 2222 false
test_inrange ':-123' 2 false
test_inrange ':-456' -222 false
test_inrange ':-456' -2222 true
test_inrange ':-456' 222 false
test_inrange ':456' 222 true
test_inrange ':456' 2222 false
test_inrange '@123' -222 true
test_inrange '@123' 222 true
test_inrange '@123:456' -222 true
test_inrange '@123:456' 222 false
test_inrange '@:456' 222 false
test_inrange '@:456' 2222 true
test_inrange '@~:-123' -222 false
test_inrange '@~:-123' 222 true
test_inrange '~:-123' -222 true
test_inrange '~:-123' 222 false