CODEWITHSUNDEEP
bashshell
user2041602
user2041602

Reputation: 179

BASH error on tests [[ ]]

I'd like to be able to validate that something is in the form of an IP in a bash script and I found various pieces of code online... they all have about the same structure..

#!/bin/bash


valid_ip()
{

    local  ip=$1
    echo $ip

    if [[ $ip =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
        ret=0 # is an IP
    else
        ret=1 # isn't an IP
    fi

    return $ret

}


# SCRIPT -------------------------------------

#clear the table
ipfw table 1 flush

ips=$(dig -f ./hostnames.txt +short)


# For each of the IPs check that it is a valid IP address
# then check that it does not exist in the ips file already
# if both checks pass append the IP to the file
for ip in $ips
do
    if valid_ip $ip; then 
        if grep -R "$ip" "~/Dropbox/ProxyBox Stuff/dummynet/ips.txt"; then 
                echo "$ip already exists"
            else
                echo $ip >> ips.txt

        fi
    fi

done


# get the IP's and add them to table 1
cat ips.txt | while read line; do
ipfw table 1 add $line
done

Anyway I am getting the following error

./script.sh: 18: ./script.sh: [[: not found

I can't understand why I can't complete this test... any help would be appreciated.

I call the script with 

sudo ./script.sh

I believe using sudo is contributing to the problem, but I need sudo pfor other parts of my script.

Upvotes: 1

Views: 275

Answers (1)

David W.
David W.

Reputation: 107040

Although the [[ ... ]] test is in all versions of BASH since the first release (the [[ ... ]] is taken from Kornshell), it is possible that there may be some Bourne shell compatibility setting in your version of BASH. However, the only thing I could turn up is compiling BASH without the --enable-cond-command. Try typing this:

$ /bin/bash -c help

This will print out a bunch of various help options. The ones with an asterisk next to them means that your version of BASH doesn't have that builtin command enabled.

In the end, you might have to find an alternative to this built in...

Try this:

if echo "$ip" |  egrep -q "^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$"

Note that you don't use square or double square brackets at all.

The -q option ensures that the egrep command won't print out anything. Instead, if the pattern matches, it will return a 0, and if not, it will return a 1. This will work with the if command. This is the way we use to do it back in the days of straight Bourne shell where regular expressions weren't built into the shell, and we had to hew shell scripts out of stone, and had real VT100 terminals.

By the way, in your regular expression, 500.600.700.900 will still show up as a valid IP address.

Upvotes: 1

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