start of the cpkg system for managing multiple versions of whatever on a session by session basis

.cpkg.sh

OS=$(uname -s)
LNDIR=$(which lndir)

# Setup for our OS, Linux maybe someday.
case "${OS}" in
	Linux)
		PKG_DIR="${HOME}/.custom/pkgdir/${OS}"
		GO_DIR="${HOME}/.custom/go/${OS}"
		PLATFORM="${OS}"
		SHA1=$(which sha1sum)
		MKTEMP="$(which mktemp)"
		if [ -f /etc/slackware-version ]; then
		  VERS=$(cat /etc/slackware-version|awk '{print $2}')
			PKG_DIR="${PKG_DIR}/Slackware/${VERS}"
			GO_DIR="${GO_DIR}/Slackware/${VERS}"
			PLATFORM="${OS} Slackware ${VERS}"
	  elif [ -f '/etc/arch-release' ]; then
	    VERS=$(uname -m)
	    PKG_DIR="${PKG_DIR}/Arch/${VERS}"
	    GO_DIR="${GO_DIR}/Arch/${VERS}"
	    PLATFORM="${OS} Arch ${VERS}"
		else
		  VERS=$(uname -r)
			PKG_DIR="${PKG_DIR}/Generic"
			GO_DIR="${GO_DIR}/Generic"
			PLATFORM="Linux Generic"
		fi
		C_ENTROPY="$(echo '$(date +%S)+${USER}${HOME}$(hostname)+$(dd if=/dev/urandom bs=512 count=1 2>/dev/null)')"
	  HASH="$(echo ${C_ENTROPY}|${SHA1}|awk '{print $1}')"
	;;
	FreeBSD)
		PKG_DIR="${HOME}/.custom/pkgdir/${OS}"
		GO_DIR="${HOME}/.custom/go/${OS}"
		PLATFORM="${OS}"
		SHA1=$(which sha1)
		MKTEMP="$(which mktemp) -t"
		HASH="$(echo '$(date +%S)+${USER}${HOME}$(hostname)+$(dd if=/dev/urandom bs=512 count=1 2>/dev/null)'|${SHA1})"
	;;
esac

# Build our environment
BASE_DIR="${HOME}/.custom/pkg/${HASH}"
P_DEFAULTS="${BASE_DIR}/defaults"
P_BIN="${BASE_DIR}/bin"
P_SBIN="${BASE_DIR}/sbin"
P_SHARE="${BASE_DIR}/share"
P_LIB="${BASE_DIR}/lib"
P_ETC="${BASE_DIR}/etc"
P_LIBEXEC="${BASE_DIR}/libexec"
P_LIB32="${BASE_DIR}/lib32"
P_INCLUDE="${BASE_DIR}/include"

# Just ensure that our base directories are present.
for i in ${PKG_DIR} ${GO_DIR} ${BASE_DIR} ${P_BIN} ${P_SBIN} ${P_ETC} ${P_SHARE} ${P_LIB} ${P_LIBEXEC} ${P_LIB32} ${P_INCLUDE}; do
	if [ ! -d ${i} ]; then mkdir -p ${i}; fi
done

cpkg() {
  case "${1}" in
    list|l)
      if [ -z "${2}" ]; then
        echo "Usage: ${0} ${1} <pkg>"
      else
	      echo "Versions for ${2} on ${PLATFORM}:\nDefault: $(grep ${2} ${PKG_DIR}/defaults)"
    		ls ${PKG_DIR}|grep -e "${2}-"|awk -F'-' '{print $2}'|sort
      fi
    ;;
    use|u)
      if [ ! -d ${PKG_DIR}/${2}-${3} ]; then
        echo "USAGE: ${0} ${1} <pkgname> <pkgvers>"
      else
        if [ ! -z "$(grep ${2}-${3} ${PKG_DIR}/defaults)" ]; then
          echo "${2}-${3} is already the default for this platform."
        elif [ ! -z "$(grep ${2} ${PKG_DIR}/defaults)" ]; then
          curr=$(grep ${2} ${PKG_DIR}/defaults)
          echo "Do you wish to replace ${curr} as default?"
          select ans in yes no; do
            case ${ans} in
              n|no) REPL="no";  break ;;
              y|yes) REPL="yes"; break ;;
              *) REPL="no" ; break ;;
            esac
          done
          case "${REPL}" in
            yes)
				      tmpf=$(${MKTEMP}) #mktemp -t defaults)
              grep -v ${2} ${PKG_DIR}/defaults >${tmpf}
              mv ${PKG_DIR}/defaults ${PKG_DIR}/defaults.bak
              mv ${tmpf} ${PKG_DIR}/defaults
              echo "Setting ${2}-${3} as the default for ${OS}."
              echo "${2}-${3}" >> ${PKG_DIR}/defaults
              cpkg_recycle
            ;;
          esac
        else
          echo "Setting ${2}-${3} as the default for ${OS}."
          echo "${2}-${3}" >> ${PKG_DIR}/defaults
          cpkg recycle
        fi
      fi
    ;;
    install|i) ;;
    purge|p) ;;
    recycle|r)
      printf "Please wait while the session paths are being built... "
      env rm -rf ${BASE_DIR}/*
      for i in ${P_BIN} ${P_SBIN} ${P_SHARE} ${P_LIB} ${P_ETC} ${P_LIBEXEC} ${P_LIB32} ${P_INCLUDE}; do
	      if [ ! -d ${i} ]; then mkdir -p ${i}; fi
      done
      ln -s ${BASE_DIR}/share/man ${BASE_DIR}/man
      for pkg in $(cat ${PKG_DIR}/defaults); do
        for dir in $(ls ${PKG_DIR}/${pkg}/); do
          ${LNDIR} -silent ${PKG_DIR}/${pkg}/${dir}/ ${BASE_DIR}/${dir}/ 
        done
      done
      echo "Done"
      temp=$(${MKTEMP}) #mktemp -t path)
      echo "export PATH=${P_BIN}:${P_SBIN}:${HOME}/.custom/noarch:/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:/usr/pkg/bin:/usr/pkg/sbin:/usr/X11R6/bin:/usr/X11R6/sbin:/usr/X11R7/bin:/usr/X11R7/sbin" >>${temp}
      echo "export LDFLAGS=-L${P_LIB}" >>${temp}
      echo "export CFLAGS=-I${P_INCLUDE}" >>${temp}
      source ${temp}
	    case "${OS}" in
		    FreeBSD) export MANPATH=$(manpath -q) ;;
	  	  Linux) export MANPATH="${MANPATH}:${BASE_DIR}/share/man:${BASE_DIR}/man" ;;
  	  esac
      rm -f ${temp}
    ;;
    help|h)
      echo "\nCpkg v0.4 by Mike 'Fuzzy' Partin <fuzzy@fu-manchu.org>\n"
      echo "Usage: ${0} [cmd] <opts>\n"
      echo "\tl list\t\tList versions for package <pkg> (ie: ruby)"
      echo "\tu use\t\tUse <pkg> <version> (ie: ${0} u ruby 1.9.0p0)"
      echo "\ti install\tWrapper around configure/make/make install (CONCEPTUAL)"
      echo "\tp purge\t\tRemove <pkg> <version> from your archive. (ie: ${0} p ruby 1.9.0p0)"
      echo "\tr recycle\tRebuild your session paths."
      echo "\th help\t\tShow this help message.\n"
    ;;
    usage) cpkg help ;;
    *) cpkg help ;;
  esac
}