Just type 'help log' on the console. You should get the required information. In fact here it is:
help log
The log command manages console log files.
Usage: log [<arg_list>]
-f=<file_path> | --file=<file_path>
Specifies a console log file. <file_path> is a full path specification to
a local file where all console output will be written after executing this
command. If the file does not exist, a new file will be created at the
specified path. If the file already exists, its contents will either be
truncated or preserved, depending on the specified (or implicit) state of
the -a argument (see below).
-a | --append
This argument is only used along with -f to control the log file open mode.
When specified, this argument selects the append log open mode: If the log
file already exists, its contents will be preserved and newly generated
console output will be written after the existing file data.
(default=enabled)
-t | --truncate
This argument is the inverse to -a: If the log file exists, it will be
truncated to zero length and its previous contents will be lost.
(default=disabled)
-q | --query
Prints information about the current console log file (this also happens
when no arguments are specified).
--enable
Enables console output log. If no log file is currently open, this argument
is ignored. Console output log is automatically enabled when a log file is
open with the -f argument.
--disable
Disables console output log. This argument is the inverse of --enable.
--close
Flushes and closes the current console log file. This effectively cancels
console logging until a log file is open again with the -f argument.
--flush
Flushes the current console log file: Writes all pending console output to
the log file, without closing it.
--help
Displays this help and exits.
-- bitli