source: vendor/bash/3.1-p17/examples/scripts.v2/cdhist.bash

#! /bin/bash
#
# cdhist - cd replacement with a directory stack like pushd/popd
#
# usage: cd [-l] [-n] [-] [dir]
#
# options:
#       -l      print the cd directory stack, one entry per line
#       -       equivalent to $OLDPWD
#       -n      cd to nth directory in cd directory stack
#       -s      cd to first directory in stack matching (substring) `s'
#
# arguments:
#       dir     cd to dir and push dir onto the cd directory stack
#
# If the new directory is a directory in the stack and the options selected
# it (-n, -s), the new working directory is printed
#
# If the variable CDHISTFILE is set, the cd directory stack is loaded from
# and written to $CDHISTFILE every time `cd' is executed.
#
# Note: I got this off the net somewhere; I don't know the original author
#
# Chet Ramey
# chet@po.cwru.edu      

_cd_print()
{
        echo -e "$@"
}

cd()
{
        typeset -i cdlen i
        typeset t
        
        if [ $# -eq 0 ]
        then
                set -- $HOME
        fi
        
        if [ "$CDHISTFILE" ] && [ -r "$CDHISTFILE" ] # if directory history exists
        then
                typeset CDHIST
                i=-1
                while read -r t                 # read directory history file
                do
                        CDHIST[i=i+1]=$t
                done <$CDHISTFILE
        fi
        
        if [ "${CDHIST[0]}" != "$PWD" ] && [ -n "$PWD" ]
        then
                _cdins                          # insert $PWD into cd history
        fi
        
        cdlen=${#CDHIST[*]}                     # number of elements in history
        
        case "$@" in
        -)                                      # cd to new dir
                if [ "$OLDPWD" = "" ] && ((cdlen>1))
                then
                        '_cdprint' ${CDHIST[1]}
                        builtin cd ${CDHIST[1]}
                        pwd
                else
                        builtin cd "$@"
                        # pwd
                fi
                ;;
        -l)                                     # _cdprint directory list
                ((i=cdlen))
                while (((i=i-1)>=0))
                do
                        num=$i
                        '_cdprint' "$num ${CDHIST[i]}"
                done
                return
                ;;
        -[0-9]|-[0-9][0-9])                     # cd to dir in list
                if (((i=${1#-})<cdlen))
                then
                        '_cdprint' ${CDHIST[i]}
                        builtin cd ${CDHIST[i]}
                        pwd
                else
                        builtin cd $@
                        # pwd
                fi
                ;;
        -*)                                     # cd to matched dir in list
                t=${1#-}
                i=1
                while ((i<cdlen))
                do
                        case ${CDHIST[i]} in
                        *$t*)
                                '_cdprint' ${CDHIST[i]}
                                builtin cd ${CDHIST[i]}
                                pwd
                                break
                                ;;
                        esac
                        ((i=i+1))
                done
                if ((i>=cdlen))
                then
                        builtin cd $@
                        # pwd
                fi
                ;;
        *)                                      # cd to new dir
                builtin cd $@
                # pwd
                ;;
        esac

        _cdins                                  # insert $PWD into cd history
        
        if [ "$CDHISTFILE" ]
        then
                cdlen=${#CDHIST[*]}             # number of elements in history

                i=0
                while ((i<cdlen))
                do
                        echo ${CDHIST[i]}       # update directory history
                        ((i=i+1))
                done >$CDHISTFILE
        fi
}
        
_cdins()                                        # insert $PWD into cd history
{                                               # meant to be called only by cd
        typeset -i i

        i=0

        while (( i < ${#CDHIST[*]} ))           # see if dir is already in list
        do
                if [ "${CDHIST[$i]}" = "$PWD" ]
                then
                        break
                fi
                ((i=i+1))
        done

        if (( i>22 ))                           # limit max size of list
        then
                i=22
        fi

        while (((i=i-1)>=0))                    # bump old dirs in list
        do
                CDHIST[i+1]=${CDHIST[i]}
        done

        CDHIST[0]=$PWD                          # insert new directory in list
}
        
# examples
shopt -s expand_aliases

# go to known place before doing anything
cd /

echo CDHIST: "${CDHIST[@]}"
for dir in /tmp /bin - -2 -l
do
        cd $dir
        echo CDHIST: "${CDHIST[@]}"
        echo PWD: $PWD

done

exit 0