Getting tcsh dextract-like pushd functionality in bash

Question

I love bash (4.1.2(1)-release) but I strongly prefer the way tcsh implements pushd +N with the dextract option enabled, so much so that I refuse to use bash as my default shell because of it. Has anyone implemented a dextract-like directory stack set of commands in bash or maybe I haven't figured out how to coax bash to behave like tcsh with dextract enabled?

The sticking point: The order that bash leaves the directory stack in after a pushd +N. For example:

$ cd /tmp
$ pushd a
/tmp/a /tmp
$ pushd ../b
/tmp/b /tmp/a /tmp
$ pushd ../c
/tmp/c /tmp/b /tmp/a /tmp
$ pushd +1
/tmp/b /tmp/a /tmp /tmp/c

Why does bash (and default tcsh) rotate the positions of all the other directories when I do a pushd +1? Why is this useful? (Perhaps if someone explained, I might appreciate the behavior and get used to it.) Compare to tcsh with dextract, which just extracts it and puts it on top:

% set dextract
% cd /tmp
% pushd a
/tmp/a /tmp 
% pushd ../b
/tmp/b /tmp/a /tmp 
% pushd ../c
/tmp/c /tmp/b /tmp/a /tmp 
% pushd +1
/tmp/b /tmp/c /tmp/a /tmp 

Note that the remaining order of the directories is untouched. I consider this important because it's easier to keep track in my mind when the order doesn't get rotated, and so I don't have to be always doing a dirs and searching for the directory I want.

If I were to take a crack at it, where would I start? I see there is a variable DIRSTACK, but it is not correct (it's empty when the stack has four entries), although changing it does alter the stack (not correctly though).

Answer 1

After some work and inspiration, I solved my problem:

# dextract-like pushd -- push $1'st directory to top of stack and shift rest down
function pushd {
    local t
    if [[ $1 =~ ^[-+]?[0-9]+$ ]]; then
        pos=$1
        [[ ${pos} -lt 0 ]] && ((pos=${#DIRSTACK[@]}+${pos}))
        if [[ ${pos} -gt 0 && ${pos} -lt ${#DIRSTACK[@]} ]]; then
            t="${DIRSTACK[$pos]}"
            # This is crufty. You can't put ~ in DIRSTACK, except the
            # shell will put it into position zero when it refers to your
            # own directory (not anyone else's!). So replace any occurrences.
            DIRSTACK=("" "${DIRSTACK[0]/#~/${HOME}}" "${DIRSTACK[@]:1:${pos}-1}" "${DIRSTACK[@]:${pos}+1}")
            cd "$t"
            builtin dirs -v
        else
            echo "$0: pushd: $1: directory stack index out of range" 1>&2
        fi
    else
        builtin pushd "$@" >/dev/null || return
        cd .
        builtin dirs -v
    fi
}