SET TERM ^ ;
create ExtractFileName(
    FILEPATH varchar(360) DEFAULT 'D:\Program Files\Firebird\Firebird_2_5\firebird.log' )
RETURNS (
    FILENAME varchar(360) )
AS
declare variable Loop_Break smallint default 0;
declare variable POS_BK_SLASH smallint default 0;
declare variable pathlength smallint default 0;

BEGIN

    Loop_Break = 0;
    while(0 = :Loop_Break) do begin
        select position('\' in :FilePath) from RDB$DATABASE into :POS_BK_SLASH;
        if(0 != :POS_BK_SLASH) then begin
            pathlength = char_length(FilePath);
            FileName = substring(:FilePath from :POS_BK_SLASH+1 for :pathlength - :POS_BK_SLASH + 1);
            FilePath = :FileName;
        end else begin
            Loop_Break = 1;
        end
    end
    suspend;   

END^
SET TERM ; ^