Question

Okay so what I am trying to figure out is how do I count the number of periods in a string and then cut everything up to that point but minus 2. Meaning like this:

string="aaa.bbb.ccc.ddd.google.com"

number_of_periods="5"

number_of_periods=`expr $number_of_periods-2`

string=`echo $string | cut -d"." -f$number_of_periods`

echo $string

result: "aaa.bbb.ccc.ddd"

The way that I was thinking of doing it was sending the string to a text file and then just greping for the number of times like this:

 grep -c "." infile

The reason I don’t want to do that is because I want to avoid creating another text file for I do not have permission to do so. It would also be simpler for the code I am trying to build right now.

EDIT

I don’t think I made it clear but I want to make finding the number of periods more dynamic because the address I will be looking at will change as the script moves forward.

Answer 1

If you don’t need to count the dots, but just remove the penultimate dot and everything afterwards, you can use Bash’s built-in string manuipulation.

${string%substring}
Deletes shortest match of $substring from back of $string.

Example:

$ string="aaa.bbb.ccc.ddd.google.com"
$ echo ${string%.*.*} 
aaa.bbb.ccc.ddd

Nice and simple and no need for sed, awk or cut!