This is a pretty minimal tip. The other day I was looking for a way to shorten URLs from the commandline. Now the bit.ly API expects you to authenticate before doing any shortening (I’ve not pulled apart the web ui to see if its possible without). The is.gd URL shortener has no such restrictions, so let's see some commandline URL shortening.
We start off using wget, a lovely tool which makes requesting web pages easy. I use the -q option to quiten it down and -O - to make it dump the output to stdout. Simple, classic. Note the trailing echo statement, which is for formatting only, so we get a newline after our URL.
$ wget -q -O - "http://is.gd/api.php?longurl=http://www.newint.org";echo
The other popular commandline http requesting tool is curl. We use its silent mode with -s. The call is even simpler than with wget.
$ curl -s "http://is.gd/api.php?longurl=http://www.newint.org"
Lynx is a non-graphical web browser and lets you run in "dump" mode where it will output a simplified text version of an html page to STDOUT. It uses the Java-esque single hyphen for long commandline arguments convention. It also indents the output a bit. Running the output through tr is left as an excercise for the reader.
$ lynx -dump "http://is.gd/api.php?longurl=http://www.newint.org"
The bulletproof way: with perl
I didn't mention that I have been assuming that your URL is already URI escaped (%20s for spaces and similar, see RFC 2396 for the gory details). We can make one that escapes your URI and fetches the short URL with perl. Here goes.
$ perl -MLWP::Simple -MURI::Escape -e 'print get("http://is.gd/api.php?longurl=" . uri_escape("http://www.newint.org") ) . "\n";'
I use the LWP::Simple module to run the API call and URI::Escape to, umm, escape the URI. The -e switch tells perl to evaluate the bit between the 's.