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# 1  
Old 12-05-2016
Grep in regex

Hello guys,
Here i am writing a script in bash to check for a valid URL from a file using regex
This is my input file

#my script
URL=$(grep -E -o   "^(http(s)?://)?+(w{3}\.)+([a-z0-9]{1,64}\.)+\w{2,3}" $path )

What my output is:

here it is trimming the htttp://
Help me out from this

Last edited by rbatte1; 12-05-2016 at 08:00 AM..
# 2  
Old 12-05-2016
You asked it to trim to at most 3 with {2,3}.
# 3  
Old 12-05-2016
I think you are over-simplifying the issue. I don't think that there is no way for certain to know if names exist with a regular expression. You cannot just assume that the last part of a domain name (the Top Level Domain) is a 2 or three characters only.

List of Internet top-level domains - Wikipedia

You might have to trim out the domain name from the full URL & perform a get to the real site to see if you connect. That might be the only way.
  • There may be a formal list of names of the TLDs
    • Each of those may have a list of valid names below them
      • Each of those may have a list of valid names below them
        • Each of those may have a list of valid names below them
          • Each of those may have a list of valid names below them ..............

You can see the problem. The list (if you could even build one) would be huge and would be frequently updating. Perhaps a DNS query would give you enough though.

host $extracted_domain_name >/dev/null
if [ $? -eq 0 ]
   echo "DNS entry exists"
   echo "It is an invalid domain"

Does that help?


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