gaboshlib/gaboshlib/g_calc.sh

function g_calc {

  unset g_calc_result

  # Use bc in backround for multiple bc's running much faster
  if [ -z "${g_bc_running}" ]
  then
    g_rnd=$$
    mkdir -p ${g_tmp}/${g_rnd}
    [ -p ${g_tmp}/${g_rnd}/bc-in ] || mkfifo ${g_tmp}/${g_rnd}/bc-in
    [ -p ${g_tmp}/${g_rnd}/bc-out ] || mkfifo ${g_tmp}/${g_rnd}/bc-out
    [ -p ${g_tmp}/${g_rnd}/bc-sed-in ] || mkfifo ${g_tmp}/${g_rnd}/bc-sed-in
    [ -p ${g_tmp}/${g_rnd}/bc-sed-out ] || mkfifo ${g_tmp}/${g_rnd}/bc-sed-out

    # bc stream channel
    { bc -ql <${g_tmp}/${g_rnd}/bc-in 2>&1 >${g_tmp}/${g_rnd}/bc-out & } 2>/dev/null
    exec 3>${g_tmp}/${g_rnd}/bc-in 4<${g_tmp}/${g_rnd}/bc-out

    # sed stream channel
    { sed -su 's/^\./0./; s/^-\./-0./' <${g_tmp}/${g_rnd}/bc-sed-in >${g_tmp}/${g_rnd}/bc-sed-out & } 2>/dev/null
    exec 5>${g_tmp}/${g_rnd}/bc-sed-in 6<${g_tmp}/${g_rnd}/bc-sed-out

    g_bc_running="true"
  fi 

  # do bc
  echo "scale=8; $@" >&3
  local g_bc_out
  if ! read -t 0.1 g_bc_out <&4
  then
    g_traceback "$@"
    ( exec 3<&- ) 2>/dev/null
    ( exec 4<&- ) 2>/dev/null
    ( exec 5<&- ) 2>/dev/null
    ( exec 6<&- ) 2>/dev/null
    unset g_bc_running
    return 1
  fi 

  # do sed
  echo ${g_bc_out} >&5
  local g_sed_out
  if ! read -t 0.1 g_sed_out <&6
  then
    g_traceback "$@"
    ( exec 3<&- ) 2>/dev/null
    ( exec 4<&- ) 2>/dev/null
    ( exec 5<&- ) 2>/dev/null
    ( exec 6<&- ) 2>/dev/null
    unset g_bc_running
    return 1
  fi

  # store result
  g_calc_result="${g_sed_out}"
}