Manual:FetchText.php/en

Details
fetchText.php file is a maintenance script to fetch a particular revision text from an old_id. This is used by when the   option is present.

Usage
Provide a text id (old_id from the text table) followed by a newline, and the script will output a string containing the following in order:
 * textid
 * length of text (-1 on error = failure to retrieve/unserialize/gunzip/etc)
 * text (may be empty)

Since revisions can be deleted without the actual revision text being removed, this script can also return text, which is no longer associated to any revision at all (may it be a current, historic or deleted revision).