Hack #4->Toggle Between Directories
You can toggle between the last two current directories using cd – as
shown below.
# cd /tmp/very/long/directory/structure/that/is/too/deep
# cd /tmp/subdir1/subdir2/subdir3
# cd –
# pwd
/tmp/very/long/directory/structure/that/is/too/deep
# cd –
# pwd
/tmp/subdir1/subdir2/subdir3# cd –
# pwd
/tmp/very/long/directory/structure/that/is/too/deep