saving authority modif in a text file. This will be used soon with another script (in crontab). The script in crontab will retrieve every authorityid in the directory localfile/authorities and modify every biblio using this authority. Those modifs may be long. So they can't be done through http, because we may encounter a webserver timeout, and kill the process before end of the job.
So, it will be done through a cron job.
(/me agree we need some doc for command line scripts)