Pro cidr2mask and mask2cidr scripts - Revision history

Nighthawk at 14:04, 28 August 2013

2013-08-28T14:04:55Z

Nighthawk at 14:02, 28 August 2013

2013-08-28T14:02:26Z

Nighthawk at 14:01, 28 August 2013

2013-08-28T14:01:59Z

Nighthawk at 14:01, 28 August 2013

2013-08-28T14:01:45Z

Nighthawk at 14:01, 28 August 2013

2013-08-28T14:01:22Z

Nighthawk at 13:59, 28 August 2013

2013-08-28T13:59:57Z

Nighthawk at 13:47, 28 August 2013

2013-08-28T13:47:50Z

Nighthawk: Pushed from thelinuxwiki.com.

2013-02-25T19:01:31Z

Pushed from thelinuxwiki.com.

New page

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

[[category:bash]]

@@ Line 4: / Line 4: @@
 == plugable bash functions==
-  # Function takes two arguments, 1st arg= netmask, 2nd arg = return variable name
+  # Function takes two arguments, 1st arg= netmask variable, 2nd arg = return variable name
   # i.e.
-  # netmask2cidr MASK CIDR<br>
+  # netmask2cidr $MASK CIDR<br>
   netmask2cidr()
+  {

@@ Line 14: / Line 14: @@
          mask="${mask%%[[:digit:]]*}"
          set -- ${#mask} ${sfx//./ }
-  <br>        # Phase 2: Convert the first non-255 number, rest is supposed to be zeroes
+  <br>       # Phase 2: Convert the first non-255 number, rest is supposed to be zeroes
          mask="0--.128.192.224.240.248.252.254."
          mask="${mask//$2*}"

@@ Line 1: / Line 1: @@
   taken from   http://forums.gentoo.org/viewtopic-p-6770850.html
- function cidr2netmask()
+== plugable bash functions==
-        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 takes two arguments, 1st arg= netmask, 2nd arg = return variable name
@@ Line 26: / Line 21: @@
          eval $returnval="'$result'"
+  }

@@ Line 44: / Line 44: @@
+}
-function netmask2cidr()
+ function netmask2cidr()
-−
+ {
          # Phase 1: Count how many 255 prefixes
          local mask="${1//255./xrandomx}" sfx=${1//255.}
@@ Line 55: / Line 55: @@
          mask="${mask//$2*}"
          echo $(( ${1} + ${#mask}/4 ))
-−
+ }
+ # Parse and validate arguments
-# Parse and validate arguments
+ [ -z "$1" ] && exit 0
-[ -z "$1" ] && exit 0
+ [ "${1%/*}" == "$1" ] && mask="$2" || mask="${1#*/}"
-[ "${1%/*}" == "$1" ] && mask="$2" || mask="${1#*/}"
+ [ -z "$mask" ] && echo "No netmask." && exit 0
-[ -z "$mask" ] && echo "No netmask." && exit 0
+ # Check and convert mask
+ ip=${1%/*}
-# Check and convert mask
+ # Convert CIDR to netmask and vice versa
-ip=${1%/*}
+ echo -n "IP: ${ip}/${mask} --> ${ip}/"
+ is_number $mask && cidr2netmask $mask || netmask2cidr $mask
 # Convert CIDR to netmask and vice versa
 echo -n "IP: ${ip}/${mask} --> ${ip}/"
 is_number $mask && cidr2netmask $mask || netmask2cidr $mask
 [[category:bash]]