shell实现netmask掩码和cidr掩码位转换

#!/bin/bash mask2cdr () { # Assumes there's no "255." after a non-255 byte in the mask local x=${1##*255.} set -- 0^^^128^192^224^240^248^252^254^ $(( (${#1} - ${#x})*2 )) ${x%%.*} x=${1%%$3*} echo $(( $2 + (${#x}/4) )) } cdr2mask () { # Number of args to shift, 255..255, first non-255 byte, zeroes set -- $(( 5 - ($1 / 8) )) 255 255 255 255 $(( (255 << (8 - ($1 % 8))) & 255 )) 0 0 0 [ $1 -gt 1 ] && shift $1 || shift echo ${1-0}.${2-0}.${3-0}.${4-0} } # examples: mask2cdr 255.255.255.0 cdr2mask 24