On Thu, 27 Jan 2000, Jeff Smelser wrote:
> Just trying to write a bash script and can't seem to figure out how to
> do addition with variables. If someone could give me a quick example, I
> would appreciate it. Thanks
Here is a script with lots of math examples.
------ cut ------
#!/bin/ksh
# Usage: ip2n <IP-Number>
Die() {
echo Bad IP
exit 1
}
[ $# = 1 ] || Die
[ ${1%%?*.?*.?*.?*} ] && Die
I=$1
until [ ${#I} = 0 ]
do
J=${I#[0-9.]}
[ ${#I} = ${#J} ] && Die
I=$J
done
I=$1.
N=0
while [ $I ]
do
J=${I%%.*}
[ $((J>>8)) = 0 ] || Die
N=$(( (N<<8) + J ))
I=${I#$J.}
done
if [ $((N < 0)) = 0 ]
then
echo $N
else
d=100000
m=$(( (1<<31) - 1 ))
u=$(( m/d ))
l=$(( m - u*d ))
v=$(( (1<<31) + N ))
x=$(( v/d ))
y=$(( v - x*d ))
s=$(( l + y + 1 ))
c=$(( s/d ))
ux=$(( u + x + c ))
ly=$(( s - c*d ))
echo ${ux}${ly}
fi
# End
------ cut ------
Cut the above and put it in a file called "ip2n", then do
the "chmod +x" thing on it then run it with the following:
ip2n 192.168.1.1
or any other IP of your choice.
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