Function to set a nice shell prompt with Pyenv and ROS shown along with a nicely trimmed current working directory

update_shell_prompt.bash

#!/bin/bash 

## Prompt setup
update_shell_prompt() {
    RED='\[\e[0;31m\]'
    GREEN='\[\e[0;32m\]'
    BLUE='\[\e[0;34m\]'
    PURPLE='\[\e[0;35m\]'
    RESET='\[\e[0m\]'

    # Check if using pyenv
    if [[ -z "${USING_PYENV}" ]]; then
	PYENV_PS1_ADD=""
    else
	[ -z "$PYENV_VIRTUALENV_ORIGINAL_PS1" ] && export PYENV_VIRTUALENV_ORIGINAL_PS1="$PS1"
	[ -z "$PYENV_VIRTUALENV_GLOBAL_NAME" ] && export PYENV_VIRTUALENV_GLOBAL_NAME="$(pyenv global)"
	VENV_NAME="$(pyenv version-name)"
	VENV_NAME="${VENV_NAME##*/}"
	GLOBAL_NAME="$PYENV_VIRTUALENV_GLOBAL_NAME"

	# non-global versions:
	COLOR="$BLUE"
	# global version:
	[ "$VENV_NAME" == "$GLOBAL_NAME" ] && COLOR="$RED"
	# virtual envs:
	[ "${VIRTUAL_ENV##*/}" == "$VENV_NAME" ] && COLOR="$GREEN"
	PYENV_PS1_ADD="[Py $COLOR${VENV_NAME}$RESET] "
    fi

    # Check if using ROS
    if [[ -z "${ROS_DISTRO}" ]]; then
	ROS_PS1_ADD=""
    else
	ROS_PS1_ADD="[ROS $PURPLE${ROS_DISTRO}$RESET] "
    fi

    # Check if in a ROS overlay
    if [[ -z "${COLCON_PREFIX_PATH}" ]]; then
	ROS_UL_PS1_ADD=""
    else
	ROS_UL_PS1_ADD="[ROS Overlay: ${BLUE}$(dirname ${COLCON_PREFIX_PATH})$RESET]\n"
    fi
    
    export PS1="${ROS_UL_PS1_ADD}[\T] ${PYENV_PS1_ADD}${ROS_PS1_ADD}$GREEN\u$RESET: $(prompt_dir_str) >> "
}
export PROMPT_COMMAND="update_shell_prompt;"


## pyenv setup
pyenv_init() {
    export PATH="$HOME/.pyenv/bin:$PATH"
    #eval "$(pyenv init - bash --no-rehash)"
    eval "$(pyenv init - )"
    eval "$(pyenv virtualenv-init -)"
    export PYENV_VIRTUALENV_DISABLE_PROMPT=1
    export USING_PYENV=1
}

## ROS Setup
ros_init() {
    source /opt/ros/foxy/setup.bash
    [[ -z "${USING_PYENV}" ]] && pyenv_init
    pyenv shell ros2-foxy
}