Really, almost completely, uninstall nix for maxOS

nix-uninstall.sh

#!/bin/bash
#

#
# snarfed from https://gist.github.com/davejamesmiller/1965569#file-ask-sh
#
ask() {
    local prompt default reply

    if [[ ${2:-} = 'Y' ]]; then
        prompt='Y/n'
        default='Y'
    elif [[ ${2:-} = 'N' ]]; then
        prompt='y/N'
        default='N'
    else
        prompt='y/n'
        default=''
    fi

    while true; do

        # Ask the question (not using "read -p" as it uses stderr not stdout)
        echo -n "$1 [$prompt] "

        # Read the answer (use /dev/tty in case stdin is redirected from somewhere else)
        read -r reply </dev/tty

        # Default?
        if [[ -z $reply ]]; then
            reply=$default
        fi

        # Check if the reply is valid
        case "$reply" in
            Y*|y*) return 0 ;;
            N*|n*) return 1 ;;
        esac

    done
}

asky() {
    ask "$1" Y
}
askn() {
    ask "$1" N
}
yon() {
    asky "execute '$1'?" && {
        # echo "executing '$1'"
        eval "$1"
    }
}

# yon "echo test logic"

#
# snarfed from https://gist.github.com/expelledboy/c00aebb004b178cf78b2c9b344526ff6
#

# !!WARNING!!
# This will DELETE all efforts you have put into configuring nix
# Have a look through everything that gets deleted / copied over

cat <<EOF
!!WARNING!!
This will DELETE all efforts you have put into configuring nix
EOF

ask "continue?" || { exit 0; }

/usr/bin/which -s nix-env && {
    nix-env -e '.*' --dry-run 2>&1 | grep -q '^uninstalling' && {
        ask "Remove previously installed?" Y && {
            nix-env -e '.*'
        }
    }
}

yonerm() {
    local rm
    rm="rm -rf"

    [[ $1 == "sudo" ]] && {
        rm="sudo $rm"
        shift
    }

    [[ -e "$1" ]] && {
        yon "${rm} $1"
    }
}

#
# XXX: This will only clean up current user
#
for x in $HOME/.nix-*; do
    yonerm "$x"
done

yonerm "$HOME/.config/nixpkgs"
yonerm "$HOME/.cache/nix"
yonerm "$HOME/.nixpkgs"

if [ -L $HOME/Applications ]; then
    # XXX: dubios
    yon "rm $HOME/Applications"
fi

yonerm "sudo" "/etc/nix"

if [ -f /Library/LaunchDaemons/org.nixos.nix-daemon.plist ]; then
    yon "sudo launchctl unload /Library/LaunchDaemons/org.nixos.nix-daemon.plist"
    yon "sudo rm /Library/LaunchDaemons/org.nixos.nix-daemon.plist"
fi

if [ -f /etc/profile.backup-before-nix ]; then
    yon "sudo mv /etc/profile.backup-before-nix /etc/profile"
fi

if [ -f /etc/bashrc.backup-before-nix ]; then
    yon "sudo mv /etc/bashrc.backup-before-nix /etc/bashrc"
fi

if [ -f /etc/zshrc.backup-before-nix ]; then
    yon "sudo mv /etc/zshrc.backup-before-nix /etc/zshrc"
fi

USERS=$(dscl . list /Users | grep nixbld)
[[ -z "$USERS" ]] || {
    asky "Cleanup nix build users?" && {
        for USER in $USERS; do
            sudo /usr/bin/dscl . -delete "/Users/$USER"
            sudo /usr/bin/dscl . -delete /Groups/staff GroupMembership $USER;
        done

        sudo /usr/bin/dscl . -delete "/Groups/nixbld"
    }
}

for x in /var/root/.nix-*; do
    yonerm sudo "$x"
done

#
# cleanup the /nix entry in /etc/fstab
#
while $(grep -q /nix /etc/fstab); do
    quit=1
    asky "Remove fstab entry?" && {
        echo "You will need to delete the /nix entry and then save the file."
        sudo vifs
        quit=0
    }
    [[ $quit ]] && break
done

grep -q /nix /etc/fstab || {
    # once this has been deleted, cleanup other stuff
    grep -q '^nix$' /etc/synthetic.conf && {
        asky "Remove 'nix' from synthetic.conf?" && {
            sudo perl -i.bkp -ne 'print unless /^nix$/' /etc/synthetic.conf
        }
    }
}

#
# remove the /nix volume
#
diskutil info "Nix Store" >/dev/null 2>&1 && {
    node=$(diskutil info "Nix Store" | awk '/Device Node/ { print $3; }')
    asky "Remove the NIX store volume ($node)?" && {
        sudo diskutil unmount $node
        sudo diskutil apfs deleteVolume $node
    }
}

exit 0

# useful for finding hanging links
# $ find . -type l -maxdepth 5 ! -exec test -e {} \; -print 2>/dev/null | xargs -I {} sh -c 'file -b {} | grep nix && echo {}'