Nslookup command line with A record IP as sole output

Question

I've found the following command to get your current public IP that works well from command line:

nslookup myip.opendns.com resolver1.opendns.com

I want to be able to run a command though that JUST prints the resulant IP. (Right now it shows the specified DNS server and it's IP along with all the other info IE:

Server:  resolver1.opendns.com
Address:  208.67.222.222

Non-authoritative answer:
Name:    myip.opendns.com
Address:  123.123.123.123

I want it to just output: 123.123.123.123

Not sure if the is a command line flag to get what I want or if I can use some command line trickery to get just the output I want (ultimately, I want to redirect the output to a file, "> filename.txt"

Solution 1

Nslookup with A record IP as sole output

Assuming you are using Windows, this can be done using a simple one line command.

From the command line:

for /f "skip=4 usebackq tokens=2" %a in (`nslookup myip.opendns.com resolver1.opendns.com`) do echo %a > ip.txt

From a batch file:

for /f "skip=4 usebackq tokens=2" %%a in (`nslookup myip.opendns.com resolver1.opendns.com`) do echo %%a > ip.txt

Notes:

• The public IP address is stored in a file (ip.txt).
• The above does not require non standard windows commands like PowerShell, .Net or awk.

---

Further Reading

• An A-Z Index of the Windows CMD command line - An excellent reference for all things Windows cmd line related.
• for /f - Loop command against the results of another command.
• nslookup - Lookup IP addresses on a NameServer.

Solution 2

nslookup was never really intended for scripted use. You really want to use dig instead, which with the +short option produces machine-readable output according to the query parameters.

dig +short myip.opendns.com @resolver1.opendns.com

Solution 3

This is a good usecase for awk.

nslookup myip.opendns.com resolver1.opendns.com | awk -F': ' 'NR==6 { print $2 } '

Here we are piping to awk, delimiting by ": " and then only outputting the second delimited field of line 6.

Solution 4

If you're on Windows, and have PowerShell installed (v1 or better) (and a .Net version) you could use a (long) one-liner like this:

[System.Net.Dns]::GetHostAddresses("www.google.com")[0] | Select IPAddressToString -ExpandProperty IPAddressToString | Out-File c:\folder\filename.txt

This will lookup www.google.com and put the first returned IPv4 address into a file.

If you're using PowerShell v3+ on Windows 8+ (or Server 2012+) you can user the use the Resolve-DnsName cmdlet instead of the .Net GetHostAddress call. ie:

(Resolve-DnsName www.google.com)[0] | Select IPAddressToString -ExpandProperty IPAddressToString | Out-File c:\folder\filename.txt

Simply change www.google.com to your preferred domain name. Or put it in a PowerShell script and set it up to accept an argument (of the domain name you want to look up).

More info on that: How to pass an argument to a PowerShell script?

Solution 5

Works good for me on my Linux machine. I've never tried it on other systems though but Google has a lot of articles on how to install dig for example on Windows

The only thing to note, for local hostnames search domain should be added explicitly. So if you have myhost host in your local network with search domain mynetwork put

dig +short myhost.mynetwork

on command line.

Examples:

sergeyi@sergeyi:~$ dig +short google.ru
173.194.222.94

sergeyi@sergeyi:~$ dig A +short google.ru
173.194.222.94

sergeyi@sergeyi:~$ dig AAAA +short google.ru
2a00:1450:4010:c0b::5e

View more solutions

Comments

[Ƭᴇcʜιᴇ007]

How do you expect to deal with names that return more than one IP address? Which OS are you using?

[Ƭᴇcʜιᴇ007]

OP hasn't specified but I'd bet he's on Windows, and there's no awk in Windows.

[MariusMatutiae]

@Techie007 But the OP has not specified he is on windows either, so we may as well provide complete information. The above answer works for all Nixes, which nicely complements other replies, including yours.

[BondUniverse]

Yes, on Windows servers.

[BondUniverse]

I need the command to work reliably on any Windows server 2003+. I agree though that if Power shell was viable, I would prefer your solution.

[Ramhound]

Why exactly is this solution not ideal? I know the answer but I normally provide an attempt to provide clarity to unclear answers before I vote on them.

[DavidPostill]

Not everybody has grep and sed` installed on their Windows PCs.

[Francisco Tapia]

and ping syntax is wrong.

[AlonL]

What's wrong with the syntax? I just wanted to give another method that I use and I thought that someone may find that useful as well. It works for me. You don't have to use it.

[zeroimpl]

This doesn't work in some cases (the hard-coded line number can be wrong). I use this instead: nslookup-ip() { nslookup "$@" | tail -n +3 | sed -n 's/Address:\s*//p' }

[Glorfindel]

Welcome to Super User! Please explain why this is a correct answer; not all of us know how to use dig.

[yass]

And it will help other users with the same problem

[StockB]

This solution is preferable over others using awk and/or sed since piping is often problematic, and it this case, unnecessarily complex.

[Jaro]

so should I use the last ouput line? In case CNAME there are two or more output lines. dig +short www.getready.cz | tail -1

[RCross]

"Assuming you are using Windows"... I'm not sure that should ever be an assumption here.

[RCross]

This is by far the best answer, as it's a cross-platform solution (ok Windows users will have to download dig) that avoids messing around with OS-specific string manipulation.

[Scott - Слава Україні]

(1) awk and sed are very powerful commands; you hardly ever need to use them together, or with grep.  The last three components of your pipeline can be reduced to two: awk '/Address/ {print $2}' | sed -n 2p or grep "Address" | awk 'NR==2 {print $2}', or even one: awk '/Address/ {if (++count==2) print $2}' or awk '/Address/ && NR==6 {print $2}'.  (2) Note that JNevill already gave an awk … 'NR==6 { print $2 }' answer.  … (Cont’d)

[Scott - Слава Україні]

(Cont’d) … (3) nslookup can output multiple matches, and the OP never specified whether they wanted all or only the first one.  How would you report all matches (i.e., lines 6 and beyond)?

[Sarita]

This actually works very well for me for a >different purpose<.

[Richard]

Add the egrep to extract the IP: dig +short my.db.host.fqdn | egrep '[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+'