Make homebrew keg-only formulae available inside a interactive subshell, by setting some PATH variables

open-keg

#!/usr/bin/env bash
set -Eeuo pipefail

# Formatting
if [[ -t 1 && $(tput colors) -ge 8 ]]; then
    _rst_="$(tput sgr0)"   ; _bol_="$(tput bold)"   ; _und_="$(tput smul)"
    _red_="$(tput setaf 1)"; _grn_="$(tput setaf 2)"; _ylw_="$(tput setaf 3)"; _blu_="$(tput setaf 4)"
else
    _rst_=""; _bol_=""; _und_=""
    _red_=""; _grn_=""; _ylw_=""; _blu_=""
fi

check_installed() {
    local not_found=()
    for keg in "${@}"; do
        if [[ -z "$(brew ls --versions "${keg}")" ]]; then not_found+=("${keg}"); fi
    done

    if [[ ${#not_found[@]} -eq 1 ]]; then
        echo "${_red_}Error:${_rst_} Keg ${_bol_}${not_found[*]}${_rst_} not found"
        exit 1
    elif [[ ${#not_found[@]} -gt 1 ]]; then 
        echo "${_red_}Error:${_rst_} Kegs ${_bol_}${not_found[*]}${_rst_} not found"
        exit 1
    fi
}

add_path() {
    if [[ -d "${2}" && ":${!1+${!1}}:" != *":${2}:"* ]]; then
        echo "🚰 Adding \"${2}\" to \$${1}"
        eval "export ${1}=\"${2}\${${1}+:\${${1}}}\""
    fi
}

open_keg() {
    local first=1;

    for keg in "${@}"; do
        if (( first )); then first=0; else echo; fi

        if ! brew info --json=v1 "${keg}" | grep -Eq '"linked_keg"\s*:\s*null\s*(,|\})'; then
            echo "${_ylw_}Warning:${_rst_} Keg ${_bol_}${keg}${_rst_} already linked, no need to open"
            continue
        fi
        
        echo "${_blu_}==>${_rst_} Opening ${_bol_}${keg}${_rst_}"
        
        local prefix
        prefix="$(brew --prefix "${keg}")"

        add_path PATH "${prefix}/bin"
        add_path ACLOCAL_PATH "${prefix}/share/aclocal"

        if [[ -d "${prefix}/lib/pkgconfig" ]]; then
            add_path PKG_CONFIG_PATH "${prefix}/lib/pkgconfig"
        else
            add_path CPATH "${prefix}/include"
            add_path LIBRARY_PATH "${prefix}/lib" 
        fi
    done
}

if [[ ${#} == 0 || ${1} == "--help" ]]; then
    echo "Usage:"
    echo "  open-keg FORMULA..."
    exit 0
fi

check_installed "${@}"
open_keg "${@}"

PS1="${_grn_}${_und_}${_bol_}|open-keg|${_rst_}"
exec /usr/bin/env bash \
    --rcfile <(echo "if [ -f ~/.bash_profile ]; then . ~/.bash_profile; elif [ -f ~/.bash_login ]; then . ~/.bash_login; elif [ -f ~/.profile ]; then . ~/.profile; fi; PS1=\"${PS1}\${PS1}\"") \
    -i