How to refresh iFile with external data source?

Anybody know how to dynamically refresh ifile used by iRules?

ifile get 
ifile listall
ifile attributes 
ifile size 
ifile last_updated_by 
ifile last_update_time 
ifile revision 
ifile checksum 
array set  [ifile attributes ]

the command of "ifile get" seems can not refresh the file configured via file management.

Any internal mechanism cashed the prior file?

The scenario is that the we retrieve update file daily or weekly from external datasource via cronb script like sftp/ftp to external server first then get the file with scheduled job and replace the file under "config/filestore/files_d/Common_d/ifile_d" invoked by iRules, thanks!

https://devcentral.f5.com/wiki/irules.iFile.ashx