Testing grep output in bash

Question

I'm looking for a way to act differently in my bash script depending on my external IP address. To be more specific if my external IP address is 111.111.111.111 then do some action, otherwise do something else.

This is my code:

extIP=$(curl ifconfig.me | grep 111.111.111.111)

if [ -? ${extIP} ]
then
    runExecutable
else
    echo "111.111.111.111 is not your IP."
fi

I don't know how to test extIP .

Answer 1

Try this

echo 'Enter the IP Address you want to test'
read IP_ADDRESS
extIP=$(curl ifconfig.me | grep -o '[0-9]*\.[0-9]*\.[0-9]*\.[0-9]*')

if [ "$IP_ADDRESS" == "$extIP" ]
then
    bash runExecutable.sh
    exit 0
fi

echo '${IP_ADDRESS} is not your IP'
exit 1 # if it's bad or just exit 0 otherwise

Answer 2

Just run the curl/grep command the check the exit status

curl ifconfig.me | grep -s 111.111.111.111
if [ "$?" == "0" ]
then 
    runExecutable
else
    echo "111.111.111.111 is not your IP."
fi

Answer 3

You should test the exit code of your command pipeline directly with if , like this:

addr="111.111.111.111"
if curl -s ifconfig.me | grep -qF "$addr"; then
    runExecutable "$addr" ...
else
    echo "$addr is not your IP."
fi

Also, you probably want to silence the curl 's progress output with -s and grep 's matches with -q , use a fixed string search in grep with -F , and store your IP address in a variable for easier later reuse.

Note the [ is actually a shell command that exits with 0 if condition that follows is true, or with 1 otherwise. if than uses that exit code for branching.

See this bash pitfall for more details.