shopt -s cmdhist # save multi lines command to one line
shopt -s no_empty_cmd_completion # no complementation with no input
shopt -s histverify # check command history before execute
+shopt -s histappend
+
+# unlimited history list
+export HISTFILESIZE=-1
+export HISTSIZE=-1
# view last 30 history or search from last 1000 history