Remove starting substring http from strings using AWK? - bash

Question

I'm wondering Is there a better and cleaner way to remove strings at beginning and last of each line in a file using AWK only?
Here's what I got so far
cat results.txt | awk '{gsub("https://", "") ;print}' | tr -d ":443"
File: results.txt
https://www.google.com:443
https://www.tiktok.com:443
https://www.instagram.com:443
To get the result
www.google.com
www.tiktok.com
www.instagram.com

Answer 1

With GNU awk.
Use / and : as field separators and print fourth column:
awk -F '[/:]' '{print $4}' results.txt
Or use https:// and : as field separators and print second column:
awk -F 'https://|:' '{print $2}' results.txt
Output:
www.google.com
www.tiktok.com
www.instagram.com

Answer 2

If it's a list of URLs like that, you could take advantage of the fact that the field separator in awk can be a regular expression:
awk -F':(//)?' '{print $2}'
This says that your field seperator is ": optionally followed by //", which would split each line into:
[$1] http
[$2] www.google.com
[$3] 443
And then we print out only field $2.

Answer 3

cat results.txt | awk '{gsub("https://", "") ;print}' | tr -d ":443"
I think you are misunderstading what tr -d does, it is used to delete enumerated characters (not substring), it does seems to do what you want because your test input
https://www.google.com:443
https://www.tiktok.com:443
https://www.instagram.com:443
do not contain : or 4 or 3 which should be kept, if you need test case which will shown malfunction try
https://www.normandy1944.info:443
Also code as above feature anti-pattern known as useless use of cat as GNU AWK can deal with file on its' own that is
cat results.txt | awk '{gsub("https://", "") ;print}'
can be written more succintly as
awk '{gsub("https://", "") ;print}' results.txt
I would rewrite whole your code (cat,awk,tr) to single awk as follows
awk '{gsub("^https://|:443$","");print}' results.txt
Explanation: replace https:// following start of line (^) or (|) :443 before end of line ($) using empty string (i.e. delete these parts) then print. Note that ^ and $ will prevent deleting https:// and :443 in middle of strings, though feel free to remove ^ and $ if you find these to be unlikely.