This optional parameter is used to alter the format of the failed accounting log file from the standard radius format when AcctLogFileFormatHook is not defined. AcctLogFileFormat is a string containing special formatting characters. It specifies the format for each line to be printed to the accounting log file. A new line is automatically appended. It is most useful if you use the %{attribute} style of formatting characters (to print the value of the attributes in the current packet.

AcctLogFileFormat %{Timestamp} %{Acct-Session-Id}\
%{User-Name}