$ help history
-d offset delete the history entry at offset OFFSET.
-a append history lines from this session to the history file
-n read all history lines not already read from the history file
-r read the history file and append the contents to the history
list
-w write the current history to the history file and append them
to the history list
Item -d above lists its argument but the others don't. The others should
say
-a [filename] append history lines from this session to the history file
-n [filename] read all history lines not already read from the history
file
-r [filename] read the history file and append the contents to the
history list
-w [filename] write the current history to the history file and append
them to the history list
