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You may find out your IP using commands like ifconfig, but if your computer is behind a firewall, that is not the IP that the world sees. Here’s a quick how-to to find out what your external IP is.

First, let’s create an alias: (link)

Next time when you need the public IP of your computer, just type getip in the command line and hit enter.

The above command gets the IP from http://whatismyip.com/automation/n09230945.asp (just copy and paste this URL to your location bar and hit enter, and see what it does!). The “-q” is to suppress verbose information (quiet mode) and “-O -” causes the output to be written to STDOUT.

You may use dyndns.org too to find out the IP, but in this case you may need some trimming: substitute the text within the code above by the following:

wget http://checkip.dyndns.org/ -O - -o /dev/null | cut -d: -f 2 | cut -d\< -f 1

A few words about various flags above:
The output of the first command (everything before the first pipe) is

<code><html><head><title>Current IP Check</title></head><body>Current IP Address: xxx.xxx.xx.xx</body></html>

(the actual IP address is masked by x).
The “-o /dev/null“ part redirects the STDERR of wget to /dev/null. The “-d :” option in first “cut” tells it to use colon (:) to be used as the delimiter and “-f 2” causes it to print second of the delimited fields. Similarly, the flags of the second “cut” cause it to use “<” as the delimiter for the piped output from the first “cut” and choose the first of the delimited fields.

UPDATE: Another one using curl [link]. You may again change the quoted text within the alias above by the following:

curl --connect-timeout 3 http://www.whatismyip.org/