Shell checks the legality of IP addresses and the legality of network masks.

Sometimes we need to check the correctness of IP input and the correctness of the network mask, written in shell script:

# Verify IP address correctness check_ip_format () {echo $1 | grep "^ [0-9] \ {1, 3 \}\. [0-9] \ {1, 3 \}\. [0-9] \ {1, 3 \}\. [0-9] \ {1, 3 \} $ ">/dev/null if [$? = 1]; thenreturn 1 else a = 'echo $1 | awk-f. '{print $1}' 'B = 'echo $1 | awk-f. '{print $2}' C = 'echo $1 | awk-f. '{print $3} 'd = 'echo $1 | awk-f. '{print $4}' If [$ A-ge 255-o $ A-Le 0-o $ B-GT 255-o $ B-lt 0-o $ C -GT 255-o $ C-lt 0-o $ D-GT 255-o $ D-Le 0]; thenreturn 2; FI # verify whether the multicast address is [$ A-ge 224-A $ A-Le 239]; thenreturn 3fi # verify the loop if [$ A-EQ 127]; thenreturn 4 fifireturn 0} # convert a number to a binary number D2b () {num = "$1" d2b = 'echo "obase = 2; $ num" | BC 'echo $ d2b} # verify the correctness of the mask check_mask_format () {echo $1 | grep "^ [0-9] \ {1, 3 \}\. [0-9] \ {1, 3 \}\. [0-9] \ {1, 3 \}\. [0-9] \ {1, 3 \} $ ">/dev/null if [$? = 1]; thenreturn 1fia = 'echo $1 | awk-f. '{print $1}' 'B = 'echo $1 | awk-f. '{print $2}' C = 'echo $1 | awk-f. '{print $3} 'd = 'echo $1 | awk-f. '{print $4} 'a = 'd2b $ a' B = 'd2b $ B' c = 'd2b $ C' d = 'd2b $ D' for I in $ A $ B $ C $ D; do [[$ I! = 0 & $ {# I }! = 8] & return 2 donemask = $ A $ B $ C $ d [["$ mask" = ~ ^ 1 [1] * [0] * $] | return 3 return 0}