need to break IP address stored in bash variable into octets - regex

Question

i've got a bash variable that contains an IP address (no CIDR or anything, just the four octets).
i need to break that variable into four separate octets like this:
$ip = 1.2.3.4;
$ip1 = 1
$ip2 = 2
# etc
so i can escape the period in sed. is there a better way to do this? is awk what i'm looking for?

Answer 1

You could use bash. Here's a one-liner that assumes your address is in $ip:
IFS=. read ip1 ip2 ip3 ip4 <<< "$ip"
It works by setting the "internal field separator" for one command only, changing it from the usual white space delimiter to a period. The read command will honor it.

Answer 2

If you want to assign each octet to its own variable without using an array or a single variable with newline breaks (so you can easily run it through a for loop), you could use # and % modifiers to ${x} like so:
[ 20:08 jon#MacBookPro ~ ]$ x=192.160.1.1 && echo $x
192.160.1.1
[ 20:08 jon#MacBookPro ~ ]$ oc1=${x%%.*} && echo $o1
192
[ 20:08 jon#MacBookPro ~ ]$ x=${x#*.*} && echo $x
160.1.1
[ 20:08 jon#MacBookPro ~ ]$ oc2={x%%.*} && echo $o2
160
[ 20:08 jon#MacBookPro ~ ]$ x=${x#*.*} && echo $x
1.1
[ 20:08 jon#MacBookPro ~ ]$ oc3=${x%%.*} && echo $o3
1
[ 20:08 jon#MacBookPro ~ ]$ x=${x#*.*} && echo $x
1
[ 20:08 jon#MacBookPro ~ ]$ oc4=${x%%.*} && echo $oc4
1
[ 20:09 jon#MacBookPro ~ ]$ echo "$oc1\.$oc2\.$oc3\.$oc4"
192\.160\.1\.1
See this /wiki/Bash:_Append_to_array_using_while-loop
and more in this article.

Answer 3

You can split strings using the set built-in, with IFS as separator (normally space and tab).
splitip () {
local IFS
IFS=.
set -- $*
echo "$#"
}
splitip 12.34.56.78
# Now $1 contains 12, $2 contains 34, etc
If you just need to backslash-escape the dots, use string substitution - bash has ${ip//./\\.}

Answer 4

This code is something that I found on another site when I was looking to do the same thing. Works perfectly for my application.
read ICINGAIPADDRESS
# The following lines will break the ICINGAIPADDRESS variable into the four octets
# and assign each octet to a variable.
ipoct1=$(echo ${ICINGAIPADDRESS} | tr "." " " | awk '{ print $1 }')
ipoct2=$(echo ${ICINGAIPADDRESS} | tr "." " " | awk '{ print $2 }')
ipoct3=$(echo ${ICINGAIPADDRESS} | tr "." " " | awk '{ print $3 }')
ipoct4=$(echo ${ICINGAIPADDRESS} | tr "." " " | awk '{ print $4 }')

Answer 5

The easier way is using AWK:
echo 192.168.0.12 | awk -F. '{print $1 $2 $3 $4}'
-F is a field separator, in this case we use the dot "." as separator and print each column individually.
mortiz#florida:~/Documents/projects$ echo 76.220.156.100 | awk -F. '{print $1 $2 $3 $4}'
76220156100
mortiz#florida:~/Documents/projects$ echo 76.220.156.100 | awk -F. '{print $1}'
76
mortiz#florida:~/Documents/projects$ echo 76.220.156.100 | awk -F. '{print $2}'
220
mortiz#florida:~/Documents/projects$ echo 76.220.156.100 | awk -F. '{print $3}'
156
mortiz#florida:~/Documents/projects$ echo 76.220.156.100 | awk -F. '{print $4}'
100