Add/remove path from the PATH environment variable

pathenv_in_ham.sh

pathenv_add() {
    if [ ! -d "$1" ]; then
        return 0
    fi
    DIR=$(unxpath "$1")
    if [ -z "$PATH" ]; then
      PATH=$DIR
    elif [ -d "$DIR" ] && [[ ":$PATH:" != *":$DIR:"* ]] ; then
        if [ "$2" = "after" ] ; then
            export PATH=$PATH:$DIR
        else
            export PATH=$DIR:$PATH
        fi
    fi
}

pathenv_remove() {
    local D=":${PATH}:";
    [ "${D/:$1:/:}" != "$D" ] && PATH="${D/:$1:/:}";
    PATH="${PATH/#:/}";
    export PATH="${PATH/%:/}";
}

pathenv_remove_add() {
    pathenv_remove "$1"
    pathenv_add "$1" "$2"
}

pathenv_stackoverflow.sh

# From: https://unix.stackexchange.com/a/479316

# Calling example:
#   append_to PATH "/usr/local/bin"

function remove_from()
{
    local path="${1}"
    local dir="${2}"
    local -a dirs=()
    local old_ifs="${IFS}"
    IFS=":"
    set -- ${!path}
    while [ "$#" -gt "0" ]
    do
        [ "${1}" != "${dir}" ] && dirs+=("${1}")
        shift
    done
    eval "export ${path}=\"${dirs[*]}\""
    IFS="${old_ifs}"
}

function append_to()
{
    remove_from "${1}" "${2}"
    [ -d "${2}" ] || return
    if [ -n "${!1}" ]
    then
        eval "export ${1}=\"${!1}:${2}\""
    else
        eval "export ${1}=\"${2}\""
    fi
}

function prepend_to()
{
    remove_from "${1}" "${2}"
    [ -d "${2}" ] || return
    if [ -n "${!1}" ]
    then
        eval "export ${1}=\"${2}:${!1}\""
    else
        eval "export ${1}=\"${2}\""
    fi
}