user@mj:~/var/www/html/mag/something/else/forever$

user@mj:/var/www/html/mag/something/else/forever$

user@mj:~/var/www/html/mag/something/else/forever$ cd /var/www/html/mag/something/else/forever

echo $(pwd | sed "s#^$HOME##")

alias cdroot='cd $(pwd | sed "s#^$HOME##")'

function cdroot() {
[[ $PWD =~ $HOME* ]] && cd $(pwd | sed "s#^$HOME##") ||
cd $(pwd | sed "s#^#$HOME#")
}

zanna@toaster:~/var/log/apt$ cdroot
zanna@toaster:/var/log/apt$ cdroot
zanna@toaster:~/var/log/apt$

$ mkdir -p var/lib
$ pwd
/home/xieerqi
$ cd var/lib
$ pwd
/home/xieerqi/var/lib
$ echo  ${PWD##*$HOME}
/var/lib
$ cd  "${PWD##*$HOME}"
$ pwd
/var/lib

$ function trimcd(){ var="${PWD##*$HOME}" ; var=${var:-/} ; cd "$var";}
$ pwd
/home/xieerqi
$ trimcd
$ pwd
/

$ function trimcd(){ var="${PWD##*$HOME}" ;[ "$var" = "/" ] && var="$HOME";var=${var:-/} ; cd "$var";}
$ pwd
/
$ trimcd
$ pwd
/home/xieerqi
$ trimcd
$ pwd
/
$ cd ~/var/lib
$ trimcd
$ pwd
/var/lib