Pro cidr2mask and mask2cidr scripts
From thelinuxwiki
taken from http://forums.gentoo.org/viewtopic-p-6770850.html
function cidr2netmask() {
local maskpat="255 255 255 255" local maskdgt="254 252 248 240 224 192 128" set -- ${maskpat:0:$(( ($1 / 8) * 4 ))}${maskdgt:$(( (7 - ($1 % 8)) * 4 )):3} echo ${1-0}.${2-0}.${3-0}.${4-0}
}
function netmask2cidr() {
# Phase 1: Count how many 255 prefixes local mask="${1//255./xrandomx}" sfx=${1//255.} mask="${mask%%digit:*}" set -- ${#mask} ${sfx//./ }
# Phase 2: Convert the first non-255 number, rest is supposed to be zeroes mask="0--.128.192.224.240.248.252.254." mask="${mask//$2*}" echo $(( ${1} + ${#mask}/4 ))
}
Here's the complete script to test these two functions and examples: cidrnetmask.sh:
- !/bin/sh
- Script: cidrnetmask.sh
- By Vince C <v_cadet AT yahoo.fr>.
- Released under the WTFPL :D .
function is_number() {
[ -n "${1}" ] && [ -z "${1//digit:}" ]
}
function cidr2netmask() {
local maskpat="255 255 255 255" local maskdgt="254 252 248 240 224 192 128" set -- ${maskpat:0:$(( ($1 / 8) * 4 ))}${maskdgt:$(( (7 - ($1 % 8)) * 4 )):3} echo ${1-0}.${2-0}.${3-0}.${4-0}
}
function netmask2cidr() {
# Phase 1: Count how many 255 prefixes local mask="${1//255./xrandomx}" sfx=${1//255.} mask="${mask%%digit:*}" set -- ${#mask} ${sfx//./ }
# Phase 2: Convert the first non-255 number, rest is supposed to be zeroes mask="0--.128.192.224.240.248.252.254." mask="${mask//$2*}" echo $(( ${1} + ${#mask}/4 ))
}
- Parse and validate arguments
[ -z "$1" ] && exit 0 [ "${1%/*}" == "$1" ] && mask="$2" || mask="${1#*/}" [ -z "$mask" ] && echo "No netmask." && exit 0
- Check and convert mask
ip=${1%/*}
- Convert CIDR to netmask and vice versa
echo -n "IP: ${ip}/${mask} --> ${ip}/" is_number $mask && cidr2netmask $mask || netmask2cidr $mask