#!/bin/sh

# This will ensure that entries only appear once (for the most
# recent time in the sequence) in ~/.directory_history.  This
# loses a lot of history, so be sure it's what you want.  For
# the moment, my use case for that file is basic the h() function
# in ~/.sh_common for navigating dirs, so this is fine.

# Will totally break if a filename contains a newline.

# See moreutils for sponge(1).

# reverse order,
# print only the first instance of a line,
# reverse order again,
# write back to the file
tac ~/.directory_history | unsorted-unique | tac | sponge ~/.directory_history