oh-my-zsh/tools/theme_chooser.sh

#!/bin/sh

# Zsh Theme Chooser by fox (fox91 at anche dot no)
# This program is free software. It comes without any warranty, to
# the extent permitted by applicable law. You can redistribute it
# and/or modify it under the terms of the Do What The Fuck You Want
# To Public License, Version 2, as published by Sam Hocevar. See
# http://sam.zoy.org/wtfpl/COPYING for more details.

THEMES_DIR="$ZSH/themes"
FAVLIST="${HOME}/.zsh_favlist"

function noyes() {
    read -p "$1 [y/N] " a
    if [[ $a == "N" || $a == "n" || $a = "" ]]; then
        return 0
    fi
    return 1
}

function theme_preview() {
    THEME=$1
    export ZDOTDIR="$(mktemp -d)"

cat <<-EOF >"$ZDOTDIR/.zshrc"
    source ~/.zshrc
    source "$THEMES_DIR/$THEME"
EOF
    zsh
    rm -rf "$ZDOTDIR"

    echo
    noyes "Do you want to add it to your favourite list ($FAVLIST)?" || \
          echo $THEME >> $FAVLIST
    echo
}

echo
echo "╺━┓┏━┓╻ ╻   ╺┳╸╻ ╻┏━╸┏┳┓┏━╸   ┏━╸╻ ╻┏━┓┏━┓┏━┓┏━╸┏━┓"
echo "┏━┛┗━┓┣━┫    ┃ ┣━┫┣╸ ┃┃┃┣╸    ┃  ┣━┫┃ ┃┃ ┃┗━┓┣╸ ┣┳┛"
echo "┗━╸┗━┛╹ ╹    ╹ ╹ ╹┗━╸╹ ╹┗━╸   ┗━╸╹ ╹┗━┛┗━┛┗━┛┗━╸╹┗╸"
echo

for i in $(ls $THEMES_DIR); do
    echo "Now showing theme $i"
    theme_preview $i
done