preserve bash history
# Maximum number of history lines in memory
export HISTSIZE=50000
# Maximum number of history lines on disk
export HISTFILESIZE=50000
# Ignore duplicate lines
export HISTCONTROL=ignoredups:erasedups
# When the shell exits, append to the history file
# instead of overwriting it
shopt -s histappend
# After each command, append to the history file
# and reread it
export PROMPT_COMMAND="${PROMPT_COMMAND:+$PROMPT_COMMAND$'n'}history -a; history -c; history -r"