Remove any potential special characters or spaces from an IP address using AWK

Got stuck earlier in an interesting regex mystery and I command-line FU’d an AWK Solution.

PROBLEM

I want to strip out all spaces and/or special characters from an IP address

PROCESS

I know how to validate an IP address no problem..

Good IPO

# echo 192.168.1.122 |egrep -q  '[[:digit:]]{1,3}\.[[:digit:]]{1,3}\.[[:digit:]]{1,3}\.[[:digit:]]{1,3}'; echo $?
0

Bad IP

# echo 192.168.xxx.111  |egrep -q '[[:digit:]]{1,3}\.[[:digit:]]{1,3}\.[[:digit:]]{1,3}\.[[:digit:]]{1,3}'; echo $?
1

However..

What if am gathering user input via script and I want to strip out any and ALL characters except the numeric IP Address!

For example,

If IP

' _192. 168.122.35'_   "

And I want to only display

192.168.122.35

Leading/trailing spaces can be stripped no problem, but it will still print the special characters

# echo "   _192. 168.122.35'_   "|awk '{gsub(/^[[:space:]]+|[[:space:]]+$/,"",$0); print}'
_192. 168.122.35'_
#

SOLUTION

I put together the following awk script to strip out everything and ONLY print the IP address.

awk -F "." '{for (i=1;i<=NF;i++) {sub("[^[:digit:]]+", "", $i);gsub(/^[[:space:]]+|[[:space:]]+$/,"",$i);if (i < NF) {p="."}else{p=""}  ;printf $i p}}'

Example

#  echo ' _ 192 .168 .120.111 "@  '|awk -F "." '{for (i=1;i<=NF;i++) {sub("[^[:digit:]]+", "", $i);gsub(/^[[:space:]]+|[[:space:]]+$/,"",$i);if (i < NF) {p="."}else{p=""}  ;printf $i p}}'
192.168.120.111
#

To put it all together in a quick script called ‘btest’

#!/bin/bash
if [ $# != 0 ]; then
        if [ $(echo "$1"  |egrep -q '[[:digit:]]{1,3}\.[[:digit:]]{1,3}\.[[:digit:]]{1,3}\.[[:digit:]]{1,3}'; echo $?) == 0 ]; then
                echo "Validated IP address [$1]"
                IP=$(echo "$1"|awk -F "." '{for (i=1;i<=NF;i++) {sub("[^[:digit:]]+", "", $i);gsub(/^[[:space:]]+|[[:space:]]+$/,"",$i);if (i < NF) {p="."}else{p=""}  ;printf $i p}}')
                echo "Corrected IP Address=$IP"
        else
                echo "Invalid IP address [$1]"
        fi

else
        echo "Enter IP address"
fi

If we were to enter an IP address of “192.168.1.11′” which contains a ‘tick’ at the end , the initial Validation would succeed.

But I can then show you how we use awk to strip out any misc characters

# ./btest "192.168.1.11'"
Validated IP address [192.168.1.11']
Corrected IP Address [192.168.1.11]

If we were to add leading and trailing white spaces on the argument we can see that it is still corrected

# ./btest " 192.168.1.11' "
Validated IP address [ 192.168.1.11' ]
Ensuring IP does not have any special characters or spaces
Corrected IP Address [192.168.1.11]

If we type an invalid IP Address we see it is caught

# ./btest " 192.168.1.xx' "
Invalid IP address [ 192.168.1.xx' ]

If I got extra wild and crazy and used the following for an IP address we would see it would still succeed

# ./btest ' _ 192.168.120.111 "@  '
Validated IP address [ _ 192.168.120.111 "@  ]
Corrected IP Address [192.168.120.111]

Now to put it all together into a script that will gather user input

#!/bin/bash
e=0
while [ $e == 0 ]; do
        printf "Enter IP address > "
        read ip
        if [ ! -z "$ip" ]; then
                if [ $(echo "$ip"  |egrep -q '[[:digit:]]{1,3}\.[[:digit:]]{1,3}\.[[:digit:]]{1,3}\.[[:digit:]]{1,3}'; echo $?) == 0 ]; then
                        echo "Validated IP address [$ip]"
                        ip=$(echo "$ip"|awk -F "." '{for (i=1;i<=NF;i++) {sub("[^[:digit:]]+", "", $i);gsub(/^[[:space:]]+|[[:space:]]+$/,"",$i);if (i < NF) {p="."}else{p=""}  ;printf $i p}}')
                        echo "Corrected IP Address [$ip]"
                        e=1
                else
                        echo "Invalid IP address [$ip]"
                        e=0
                fi

        else
                echo "ERROR: Enter IP address"
        fi
done

Example 1

# ./btest
Enter IP address > 192.168.1.222
Validated IP address [192.168.1.222]
Corrected IP Address [192.168.1.222]

Example 2

# ./btest
Enter IP address > '192.168.122.111 '
Validated IP address ['192.168.122.111 ']
Ensuring IP does not have any special characters or spaces
Corrected IP Address [192.168.122.111]