How to get a computer's internet (IP address) location using command line?

There's a service providing this: ipinfo.io.

You can invoke it using curl. Example:

curl ipinfo.io

Result:

{
  "ip": "...",
  "hostname": "...",
  "city": "...",
  "region": "...",
  "country": "...",
  "loc": "...,...",
  "org": "..."
}

A specific IP's info can also be requested: curl ipinfo.io/216.58.194.46:

{
  "ip": "216.58.194.46",
  "hostname": "dfw25s12-in-f14.1e100.net",
  "city": "Mountain View",
  "region": "California",
  "country": "US",
  "loc": "37.4192,-122.0574",
  "org": "AS15169 Google Inc.",
  "postal": "94043"
}

Source: http://xmodulo.com/geographic-location-ip-address-command-line.html

Since the question doesn't specify an OS, this is how to get that same information with PowerShell's curl (actually an alias of Invoke-WebRequest):

(curl ipinfo.io).Content

That produces a JSON string. To get the object that JSON represents, use ConvertFrom-Json:

curl ipinfo.io | ConvertFrom-Json

Since that's a PowerShell object, you can easily get specific fields from it. For example, this command gets just the external IP as a string:

(curl ipinfo.io | ConvertFrom-Json).ip

Note that the geographical information from this service isn't super accurate, but it did locate me within 20 miles or so. The ISP information seems to be reliable.