cleanup ~/.bash_history by removing repeated entries from top to bottom

cleanup_hist.sh

#!/bin/bash
#@brief: shorten ~/.bash_history by removing repeated entries from top to bottom (keep last)
#this additionaly cleanup because below setting not work properly
#HISTCONTROL=ignoreboth:erasedups #ignoreboth(^space and consecutive duplicates), remove duplicates
#@note: this script not work with HISTTIMEFORMAT enable (command with timestamp)

#declare filepath
HIST=$HOME/.bash_history
TEMP=/tmp/tmp_hist

#1. output history in reversed order
#2. remove all repeated entries except first one then store in /tmp if succeed
#   First time a specific value of a line ($0) is seen, the value of x[$0] is zero
#   The value of zero is inverted with '!' to one
#   An statement that evaluates to one causes the default action, which is printed
#   Every next time, the value of x[$0] has been incremented. It negated value to zero and doesn't print
#   So to keep first command instead using: awk '!x[$0]++' ~/.bash_history
#3. write inversed temporare history ('top' again back to 'bottom') into history file
#4. delete tmp file if everything succeed
tac $HIST | awk '!x[$0]++' > $TEMP && tac $TEMP > $HIST && rm $TEMP

#reverse output (tac) is not available on mac os. Consider install coreutils or using longer command:
#cat $HIST | nl | sort -k2 -k 1,1nr | uniq -f1 | sort -n | cut -f2 > $TEMP && cat $TEMP > $HIST && rm $TEMP