I'm trying to remove log files older than 48hours.

I read that i should use now()-seconds as the datetime, so i'll try

file_remove('filepath',now() - 172800) ;

file_remove(filepath, (now()-172800)) ;

boh failed with message : nxlog.conf; syntax error, unexpected TOKEN_INTEGER

in the doc, it's specified that datetime-integer return a datetime, but when i check with

file_remove('filepath',now()) ;

i don't get the syntax error. 

then, i used 

file_remove('filepath', datetime(now()-172800)); i also get the syntax error unexpected TOKEN_INTEGER.

How can i specify to file_remove the 'older' parameter to "48h" ?