keep bash history forever

.bashrc

@@ -6,12 +6,16 @@
 export HISTCONTROL=$HISTCONTROL${HISTCONTROL+,}ignoredups
 # ... or force ignoredups and ignorespace
 export HISTCONTROL=ignoreboth
+# never truncate bash history file
+export HISTFILESIZE=
+export HISTSIZE=
+export HISTTIMEFORMAT="[%F %T] "
+# always write a history line
+export PROMPT_COMMAND="history -a; $PROMPT_COMMAND"
 
 # append to the history file, don't overwrite it
 shopt -s histappend
 
-# for setting history length see HISTSIZE and HISTFILESIZE in bash(1)
-
 # check the window size after each command and, if necessary,
 # update the values of LINES and COLUMNS.
 shopt -s checkwinsize