Hi all, the value in the following file is just an example. It could be a different value/network addresses.
Here is my example of initial output in a file name net.txt
Initial Output, net.txt
The goal is to produce the following format which is to convert from CIDR to Netmask formatting.
My current draft script which is not perfect is to use �sed� to replace �/24� with �255.255.255.0� format. This is part of network subnetting conversion.
This is to print the initial net.txt value and save the final output to net-mask.txt
or
Or course the sed script for CIDR to netmask table above is not complete. The full list of the conversion can be found here. Netmask / CIDR Translation Table
Please let me know where is the best place to put �sed� into my shell script file.
If there is better way to do this, please let me know. Thanks in advance.
EDIT: Also kindly use code tags for commands and codes not quotes, quotes you can use to address any user's speicific post etc purposes like I have used above for your post, you can go through the forum rules in below link.
There is a syntax error in the above code: The quote in front of $1 is superfluous.
Apart from that, in this particular case (input file contains only one column) the above code is essentially the same as cp net.txt net-mask.txt
If you plan to use it for modification of net-mask.txt, then it certainly should be placed below the awk command.
#!/bin/bash
awk '{
print $1;
}' net.txt > net-mask.txt
sed -i 's/\/8/ 255.0.0.0/' net-mask.txt
sed -i 's/\/16/ 255.255.0.0/' net-mask.txt
sed -i 's/\/24/ 255.255.255.0/' net-mask.txt
Note I used sed 's -i option for inplace editing, otherwise things get complicated, e.g.
sed 's/\/8/ 255.0.0.0/' net-mask.txt > net-mask.temp
mv net-mask.temp net-mask.txt
sed 's/\/16/ 255.255.0.0/' net-mask.txt > net-mask.temp
mv net-mask.temp net-mask.txt
sed 's/\/24/ 255.255.255.0/' net-mask.txt > net-mask.temp
mv net-mask.temp net-mask.txt
Cool. I�ll just need to add the rest of CIDR to Netmask conversion.
I�ll share the full bash script later once it�s complete.
I�ll take note on code vs quotes. Thanks again I really appreciate it.
Next project is to reverse this process which is to convert from netmask to CIDR form
---------- Post updated at 01:34 AM ---------- Previous update was at 01:22 AM ----------
Many thanks RudiC
This forum is super cool. One question, multiple solutions provided and each of them is unique.
And here is the output
me@box:~/$ cat net.txt
10.0.0.0/8
172.16.1.0/16
192.168.1.0/24
me@box:~/$
me@box:~/$ cat ./cidr2subnet-RudiC
################################################
# Credit and special thanks to "RudiC":
# Usage: ./cidr2subnet-RudiC
################################################
while IFS="/" read A B
do DL=$'\t'
printf "%s/%s" $A $B
for i in 24 16 8 0
do printf "%s%d" "$DL" $(((2**32-1 ^ (2**(32-B)-1) >> $i) & 255))
DL="."
done
printf "\n"
done < net.txt
me@box:~/$
me@box:~/$ ./cidr2subnet-RudiC
10.0.0.0/8 255.0.0.0
172.16.1.0/16 255.255.0.0
192.168.1.0/24 255.255.255.0
me@box:~/$
I just have one question on this script. Is it possible to remove /8,/16, and /24 from the output and use a space instead of tab?
Please let me know if there is a way to reverse this process from CIDR to netmask formatting.
Example:
Initial Input
Final Output
---------- Post updated at 01:52 AM ---------- Previous update was at 01:34 AM ----------
Your solution is perfect. Thanks again. I noticed you've added "< infile > outfile" to this script. I'm new to the shell script and it's so fun learning it by solving daily problem and make things easier.
I've updated the input and output file name and here is the sample of the output. Please let me know how to reverse this process as well from netmask to CIDR formatting.
me@box:~/$ cat net.txt
10.0.0.0/8
172.16.1.0/16
192.168.1.0/24
me@box:~/$
me@box:~/$ cat cidr2subnet-Corona688
#!/bin/bash
################################################
# Credit and special thanks to "Corona688":
# Usage: ./cidr2subnet-Corona688
################################################
while IFS="/" read IP S
do
M=$(( 0xffffffff ^ ((1 << (32-S)) -1) ))
echo "$IP $(( (M>>24) & 0xff )).$(( (M>>16) & 0xff )).$(( (M>>8) & 0xff )).$(( M & 0xff ))"
done < net.txt > net-mask.txt
me@box:~/$
me@box:~/$ ./cidr2subnet-Corona688
me@box:~/$
me@box:~/$ cat net-mask.txt
10.0.0.0 255.0.0.0
172.16.1.0 255.255.0.0
192.168.1.0 255.255.255.0
me@box:~/$
To remove the /nn, replace printf "%s/%s" $A $B by printf "%s" $A
For the reverse operation, try
while IFS=" ." read -a VAL
do N=0
DL=( . . . / )
for ((J=0;J<=3;J++))
do printf "%d%s" ${VAL[J]} "${DL[J]}"
for ((I=7;I>=0;I--))
do N=$(( N + (VAL[J+4]>>I)%2 ))
done
done
printf "%d\n" $N
done < file
10.0.0.0/8
10.0.0.0/10
172.16.1.0/16
172.16.1.0/17
172.16.1.0/18
172.16.1.0/19
192.168.1.0/24
192.168.1.0/32
