This is a bash script that makes heavy use of the Linux dig utility to look up all of the authoritative nameservers on a domain name, 
then queries each server directly for any record types supported by dig (a aaaa mx soa srv etc.).  

The output of each server is compared against the others for any inconsistencies.  The script makes heavy use of text coloring to 
make problem identification easy, but this needs to be enabled in the options in the head of the script file.  

The script accepts any number of domain names and record types in any order as parameters.  As the script is not optimized to do 
simultaneous dig queries, so the more parameters that you enter, the more painfully slow it becomes.

--

Usage:
bash fi.sh example1.com example2.com a mx cname srv txt

It is useful to setup an alias like f or fish in your .bashrc or simply rename fi.sh to fish or whatever and stick it in your bin
or other directory listed in your $PATH

--

Lookup procedure:

Parsing the arguments - Any arguments passed that do not match a regular expression as being a valid domain name are assumed to be
record types.  This means you can pass arguments in any order or any number.  Multiple domain names are supported, but not usually
recommended as it can be very slow and spammy.

dig +trace - Any domain names found will first trigger a dig +trace.  The authoritative nameservers are recovered from this output.

Direct dns server queries - Each server is then queried using the `dig @ns1.example.com example1.com record` syntax.

Output comparison - Results are sorted, then compared in sequence of return using bash string equivalence conditions.  The string
comparisons are done case-insensitive as there are rare cases where DNS records are the exact same, but entered differently on
the different nameservers.  If the server's records match the previous service, it 'agrees' with it in green (assuming color
is enabled) and disagrees in red.  In the case of a disagreement, both the first and second records are printed.  This potentially
can display the records from all nameservers, but if all is good, you only see the output from a single server.

Enabling color can be done by editing your copy of the script.  There is a true/false variable near the top of the script to enable it.

Colors can be customized using the variables listed at the top of the script as well.

Known bugs:

The biggest issue is more of a problem with intuition rather than a coding bug.  When requesting a CNAME record, it is often assumed
that all records (ie. www.example.com ftp.example.com) are returned.  This is incorrect.  There is no easy way to retrieve all records
of a specific type for a domain name.  Instead you must request each subdomain exactly to check if it has a record.  If you ask the
right question, you will get the right answer.

There is also an issue with SOA records.  Currently, if you specify the record type "SOA" and it's on a sub-domain, you aren't likely
to get a result.  It's best to do SOA lookups on the raw domain name, not on any subdomains.