Posterous has a really neat feature of their API docs - you can use it directly from the web page. Unfortunately, I only need it to migrate off to Octopress.

Log into Posterous and then open the API page. Use the first entry to obtain your API token. Put this, your login and password below and you should be able to obtain a list of your Posterous Sites, or Spaces as they’re now called.

$ curl --silent -vX GET --user you@domain.com:passwd \
  -d "api_token=your_API_token" http://posterous.com/api/2/sites

* Connected to posterous.com (184.106.20.99) port 80 (#0)
* Server auth using Basic with user 'you@domain.com'
> GET /api/2/sites HTTP/1.1
> Authorization: Basic BEEFDEADXNlLm5ldC5uejp3dWJ3dWI=
> User-Agent: curl/7.21.4 (universal-apple-darwin11.0) libcurl/7.21.4 \
        OpenSSL/0.9.8r zlib/1.2.5
> Host: posterous.com
> Accept: */*
> Content-Length: 42
> Content-Type: application/x-www-form-urlencoded
>
} [data not shown]
< HTTP/1.1 200 OK
< Server: nginx/0.7.65
< Date: Tue, 13 Dec 2011 00:49:49 GMT
< Content-Type: application/json; charset=utf-8
< Connection: close
< Status: 200 OK
< X-RateLimit-Limit: 1000000
<
{ [data not shown]
* Closing connection #0

Lovely. Now that will also provide you with some output, deep inside that is a site_id field - your site. I’ve conveniently relabelled this one as 1234567:

{
      "is_private" : false,
      "hostname" : "your_posterous_site_name",
      "readers_count" : 1,
      "admins_count" : 1,
      "full_hostname" : "your_posterous_site_name.posterous.com",
      "profile_image_35" :
        "http://files.posterous.com/user_profile_pics/1357443/dch_thumb.jpg",
      "admins" : [{
            "current_user_following_info" : null,
            "firstname" : "Dave",
            "nickname" : "dch",
            "site_id" : 1234567
        }]
}

Take that site_id and bung it into this curly command, and stash your posterous content to a file. Note how I use the pages=2 parameter to retrieve the subsequent page.

$ curl --silent -X GET --user user@domain.com:passwd -d \
  "api_token=DeaDBeeFDogFooducDdoG" \
  http://posterous.com/api/2/sites/1234567/posts > /tmp/posts1.json
$ curl --silent -X GET --user user@domain.com:passwd -d \
  "api_token=DeaDBeeFDogFooducDdoG" \
  http://posterous.com/api/2/sites/1234567/posts\?pages\=2 > /tmp/posts2.json

In particular, note the headers returned by cURL - this is a simple validation that we’re on the right page, and have recovered all the data. Great!

< X-Current-Page: 2
< X-Runtime: 29
< Content-Length: 148638
< X-Total-Entries: 31
< X-Per-Page: 20
< X-Total-Pages: 2

For bonus points, next time I’ll use CouchDB’s awesome powers to convert this back into octopress format.