diff --git a/bin/tus b/bin/tus
index ff382c6..b5099d1 100755
--- a/bin/tus
+++ b/bin/tus
@@ -1,29 +1,29 @@
 #!/usr/bin/env bash
 set -e
 
-: ${TUSD:=""}
-: ${TUS_HEADERS:=''}
+: "${TUSD:=}"
+: "${TUS_HEADERS:=}"
 export TUS_CHUNK_SIZE=${TUS_CHUNK_SIZE:-1048576}
 export TUS_PARALLEL=${TUS_PARALLEL:-1}
 
 # ==============================================================================
 # debugging & usage & tus-helper
-function error { local message="${1}"; local env="${2}";
-  [ -n "${2}" ] && message="Missing ${1}. Please execute:\n"
+function error { local message="$1"; local env="$2";
+  [ -n "$2" ] && message="Missing $1. Please execute:\n"
 
-  echo -e "\033[1;31m➤\033[0m ${message}"
-  [ -n "${env}" ] \
-    && echo -e "\033[1;34mexport\033[0m ${env}=\"\033[1;31m<<${1}>>\033[0m\""
+  echo -e "\033[1;31m➤\033[0m $message"
+  [ -n "$env" ] \
+    && echo -e "\033[1;34mexport\033[0m $env=\"\033[1;31m<<$1>>\033[0m\""
   exit 1
 }
 
-function warning { local message="${1}"
-  echo -e "\033[0;33m➤\033[0m ${message}"
+function warning { local message="$1"
+  echo -e "\033[0;33m➤\033[0m $message"
 }
 
-function usage { local message="${1}";
-  [ -n "${message}" ] \
-    && echo -e "\033[0;31m➤\033[0m \033[1m${message}\033[0m"
+function usage { local message="$1";
+  [ -n "$message" ] \
+    && echo -e "\033[0;31m➤\033[0m \033[1m$message\033[0m"
   cat <<-EOTXT
 
 Usage:
@@ -39,27 +39,39 @@ Options:
   -H HEADER         Set additional header.
   -r                Reuploads given file from the beginning.
   -h                Shows usage.
+  -D                Debug.
 
 EOTXT
   echo -e "\033[2m➤ https://tus.io/protocols/resumable-upload.html\033[0m"
   echo -e "\033[2m➤ https://github.com/fentas/tus-shell-client\033[0m"
-  [ -z "${message}" ] && exit 0 || exit 1
+  [ -z "$message" ] && exit 0 || exit 1
 }
 
 # ==============================================================================
 # helper
-function ceil { local dividend="${1}"; local divisor="${2}"
-  [ $(( dividend % divisor )) -gt 0 ] \
-    && echo $(( ( ( $dividend - ( $dividend % $divisor ) ) / $divisor ) + 1 )) \
-    || echo $(( $dividend / $divisor ))
+
+# https://stackoverflow.com/a/34545932/10440128
+function ceildiv() {
+    local num=${1:-0}
+    local div=${2:-1}
+    if ! ((div)); then return 1; fi
+    if ((num >= 0)); then
+        echo $(( (num + div - 1) / div ))
+    else
+        echo $(( -(-num + div - 1) / div ))
+    fi
 }
 
-function expand { local prefix="${1}"; shift; for entry in "${@}"; do
-  [ ! -z "$entry" ] && echo -e "$prefix \"$entry\"";
-done; }
+function set_header_args() {
+  # note: nonlocal variable: header_args
+  local header
+  for header in "$@"; do
+    header_args+=("-H" "$header")
+  done
+}
 
-function strip-domain { for entry in "${@}"; do
-  [ ! -z "$entry" ] && echo -n "${entry} " | sed -E 's|^https?://[^/]+(.*)|\1|';
+function strip-domain { for entry in "$@"; do
+  [ -n "$entry" ] && echo -n "$entry " | sed -E 's|^https?://[^/]+(.*)|\1|';
 done; }
 
 function join { local IFS="$1"; shift
@@ -68,149 +80,154 @@ function join { local IFS="$1"; shift
 
 # ==============================================================================
 # tus
-tus_location=$(mktemp -u)
-mkfifo $tus_location
 
-function tus_options {
+function get_tus_options {
   # The Client SHOULD NOT include the Tus-Resumable header in the request and the Server MUST ignore the header.
-  eval "local tus_headers=($(expand '-H' "${TUS_HEADERS[@]}"))"
-  curl -s \
-    "${tus_headers[@]}" \
+  local header_args=()
+  set_header_args "${TUS_HEADERS[@]}"
+  local response
+  local rc
+  response="$(curl -s \
+    --fail-with-body \
+    "${header_args[@]}" \
     --head \
     --request OPTIONS \
-    ${TUSD} | grep 'Tus-' | tr -d '\015'
+    "$TUSD"
+  )"
+  rc=$?
+  if [ $rc != 0 ]; then
+    echo "$response" | tr -d '\r'
+    return $rc
+  fi
+  echo "$response" | grep -i '^Tus-' | tr -d '\r'
 }
 
 function tus_supports {
-  echo "${TUS_OPTIONS[@]}" | grep -qE "^Tus-Extension:.*[, ]${1}[,$]" \
-    || error "${2}.\n\033[2m↳ See tusd options: \033[1;34m${0} -o\033[0m"
+  echo "${TUS_OPTIONS[@]}" | grep -qE "^Tus-Extension:.*[, ]$1[,$]" \
+    || error "$2.\n\033[2m↳ See tusd options: \033[1;34m$0 -o\033[0m"
 }
 
 function tus_create {
-  local file="${1}"; shift
-  local size="${1}"; shift
+  local file="$1"; shift
+  local size="$1"; shift
 
-  eval "local tus_headers=($(expand '-H' "${TUS_HEADERS[@]}"))"
-  for header in "${@}"; do
-    tus_headers+=(-H "${header}")
+  local header_args=()
+  set_header_args "${TUS_HEADERS[@]}"
+  for header in "$@"; do
+    header_args+=(-H "$header")
   done
 
-  # Apparently 'Location: ..' is terminated by CRLF. grep and awk faithfully
-  # preserve the line ending, and the shell's $() substitution strips off the
-  # final LF leaving you with a string that just ends with a CR.
-  #
-  # When the CR is printed, the cursor moves to the beginning of the line and
-  # whatever gets printed next overwrites what was there.
-  # ... | tr -d '\015'
+  # Most HTTP server use '\r\n' line endings, so here we remove the '\r'
   curl -s \
-    "${tus_headers[@]}" \
+    --fail-with-body \
+    "${header_args[@]}" \
     --head \
     --request POST \
     --header "Tus-Resumable: 1.0.0" \
     --header "Content-Length: 0" \
-    --header "Upload-Length: ${size}" \
-    --header "Upload-Metadata: name $(basename "${file}" | tr -d '\n' | base64)" \
+    --header "Upload-Length: $size" \
+    --header "Upload-Metadata: name $(basename "$file" | tr -d '\n' | base64)" \
     --header "Connection: close" \
-    ${TUSD} | grep 'Location:' | awk '{print $2}' | tr -d '\015' 1> $tus_location 2>&1 &
-  return $?
+    "$TUSD" | grep -i '^Location:' | sed -E 's/^[^:]+:\s*(.*)$/\1/' | tr -d '\r'
 }
 
 function tus_upload {
   # trap 'kill $(jobs -p)' SIGINT SIGTERM
 
-  local dest="${1}"
-  local file="${2}"
-  local size="${3}"
-  local parts="${4}"
-  local multi="${5}"
-  local color=$(( $RANDOM % 7 + 31 ))
-
-  response=$(mktemp -u)
-  mkfifo $response
+  local dest="$1"
+  local file="$2"
+  local size="$3"
+  local parts="$4"
+  local multi="$5"
+  local color=$(( RANDOM % 7 + 31 ))
 
   while true; do local part=0; local finished=1
-    while [ "${part}" -lt "${parts}" ]; do
-      if ! tus_complete "${file}" "${dest}" "${part}"; then
+    while [ "$part" -lt "$parts" ]; do
+      if ! tus_complete "$file" "$dest" "$part"; then
         local offset=$(( part * TUS_CHUNK_SIZE ))
         local file_offset=$(( (multi - 1) * parts * TUS_CHUNK_SIZE ))
         local length=$(( size - file_offset - offset ))
-        [ ${length} -gt "${TUS_CHUNK_SIZE}" ] \
-          && length="${TUS_CHUNK_SIZE}"
-
-        echo -e "\033[0;32m🠹\033[0m Upload \033[1m\e[1;${color}mpart ${part}\e[0m\033[21m."
-        echo -e "\033[2m↳ ${dest}"
-        eval "local tus_headers=($(expand '-H' "${TUS_HEADERS[@]}"))"
+        if [ "$length" -gt "$TUS_CHUNK_SIZE" ]; then
+          length="$TUS_CHUNK_SIZE"
+        fi
+
+        echo -e "\033[0;32m🠹\033[0m Upload \033[1m\e[1;${color}mpart $part\e[0m\033[0m."
+        echo -e "\033[2m↳ $dest"
+        local header_args=()
+        set_header_args "${TUS_HEADERS[@]}"
         # TODO curl will throw (55: Broken pipe)
         # >> tusd will break connection after 'Content-Length'
         # >> ? curl: how to set content length to upload
 
+        response="$(
         curl --progress-bar \
-          "${tus_headers[@]}" \
+          "${header_args[@]}" \
           --write-out "%{http_code}" \
           --request PATCH \
           --header "Tus-Resumable: 1.0.0" \
           --header "Content-Type: application/offset+octet-stream" \
-          --header "Content-Length: ${length}" \
-          --header "Upload-Offset: ${offset}" \
+          --header "Content-Length: $length" \
+          --header "Upload-Offset: $offset" \
           --data-binary "@-" \
-          "${dest}" < <(dd if=${file} skip=$(( file_offset + offset )) count=${length} iflag=skip_bytes,count_bytes 2>/dev/null) 1> $response &
+          "$dest" < <(dd if="$file" skip=$(( file_offset + offset )) count="$length" iflag=skip_bytes,count_bytes status=none)
+        )"
 
-        tus_complete "${file}" "${dest}" "${part}" "$(tee < $response)"
-        echo -ne "\033[22m"
+        tus_complete "$file" "$dest" "$part" "$response"
+        echo -ne "\033[0m"
         finished=0
       fi
       part=$((part + 1))
     done
 
-    [ ${finished} -eq 1 ] && break
+    [ "$finished" = 1 ] && break
   done
-  rm $response
 }
 
 # TODO unhandled error codes
 # - 409: mismatched offset
 # - 423: file currently locked
 function tus_complete {
-  local file="${1}"
-  local dest="${2}"
-  local part="${3}"
-  local -r code="$(echo ${4} | grep -o '[[:digit:]]*$')"
-  local -r key="# 🠹 ${dest} [${part}]"
+  local file="$1"
+  local dest="$2"
+  local part="$3"
+  local -r code="$(echo "$4" | grep -o '[[:digit:]]*$')"
+  local -r key="# 🠹 $dest [$part]"
 
-  if [ -z "${code}" ]; then
+  if [ -z "$code" ]; then
     # read
-    cat "${file}.tus" | grep -qF "${key}"
+    grep -qF "$key" "$file.tus"
     return $?
-  elif [ "${code}" -eq 204 ] || [ "${code}" -eq 100 ]; then
+  elif [ "$code" = 204 ] || [ "$code" = 100 ]; then
     # TODO what to do with status_code 100 Continue?
     # write
-    echo "${key} uploaded." >> "${FILE}.tus"
+    echo "$key uploaded." >> "$FILE.tus"
   else
-    warning "\033[1m${part}\033[21m failed. Will retry.\n\033[2m↳ $(echo ${4} | tr -d '\n')\033[22m"
+    warning "\033[1m$part\033[0m failed. Will retry.\n\033[2m↳ $(echo "$4" | tr -d '\n')\033[0m"
   fi
 }
 
 function tus_concat {
-  local file="${1}"
+  local file="$1"
 
-  eval "local tus_headers=($(expand '-H' "${TUS_HEADERS[@]}"))"
+  local header_args=()
+  set_header_args "${TUS_HEADERS[@]}"
   curl -v \
-    "${tus_headers[@]}" \
+    --fail-with-body \
+    "${header_args[@]}" \
     --head \
     --request POST \
     --header "Tus-Resumable: 1.0.0" \
     --header "Content-Length: 0" \
-    --header "Upload-Concat: final;$(strip-domain "${TUSD}" "${@}")" \
-    --header "Upload-Metadata: name $(basename "${file}" | tr -d '\n' | base64)" \
+    --header "Upload-Concat: final;$(strip-domain "$TUSD" "$@")" \
+    --header "Upload-Metadata: name $(basename "$file" | tr -d '\n' | base64)" \
     --header "Connection: close" \
-    ${TUSD} | grep 'Location:' | awk '{print $2}' | tr -d '\015' 1> $tus_location 2>&1 &
-  echo $?
+    "$TUSD" | grep -i '^Location:' | sed -E 's/^[^:]+:\s*(.*)$/\1/' | tr -d '\r'
 }
 
 function tus_done {
-  local dest="${1}"
+  local dest="$1"
   echo -e "\n\033[0;32m➤ All parts uploaded 🐈\033[0m"
-  [ -n "${dest}" ] && echo -e "\033[2m↳ ${dest}\033[22m"
+  [ -n "$dest" ] && echo -e "\033[2m↳ $dest\033[0m"
   exit 0
 }
 
@@ -218,38 +235,33 @@ function tus_done {
 # main
 declare -A pids
 
-function cleanup {
-  rm $tus_location
-  # kill "${pids[@]}"
-}
-trap cleanup EXIT
-
 # ==============================================================================
 # pre
-IFS=',' read -r -a TUS_HEADERS <<< "${TUS_HEADERS}"
+IFS=',' read -r -a TUS_HEADERS <<< "$TUS_HEADERS"
 OPT_RESET=0
 OPT_OPTIONS=0
-while getopts ohrc:p:H:t: opt
+OPT_DEBUG=0
+while getopts ohrc:p:H:t:D opt
 do
-  case "${opt}" in
+  case "$opt" in
     t)
-      TUSD="${OPTARG}"
+      TUSD="$OPTARG"
     ;;
     c)
-      [ -z "${OPTARG}" ] || echo "${OPTARG}" | grep -vq '^[[:digit:]]*$' \
+      [ -z "$OPTARG" ] || echo "$OPTARG" | grep -vq '^[[:digit:]]*$' \
         && usage
       TUS_CHUNK_SIZE=$((OPTARG * 1048576))
     ;;
     p)
-      echo "${OPTARG}" | grep -vq '^[[:digit:]]*$' \
+      echo "$OPTARG" | grep -vq '^[[:digit:]]*$' \
         && usage
-      TUS_PARALLEL="${OPTARG}"
+      TUS_PARALLEL="$OPTARG"
 
-      [ ${TUS_PARALLEL} -gt 1 ] \
+      [ "$TUS_PARALLEL" -gt 1 ] \
         && tus_supports "concatenation" "Tusd can not perform parallel uploads"
     ;;
     H)
-      TUS_HEADERS+=("${OPTARG}")
+      TUS_HEADERS+=("$OPTARG")
     ;;
     r)
       OPT_RESET=1
@@ -257,23 +269,36 @@ do
     o)
       OPT_OPTIONS=1
     ;;
+    D)
+      OPT_DEBUG=1
+    ;;
     ?) usage
    esac
 done
 shift $((OPTIND - 1))
 
-[ -z "${TUSD}" ] && error 'tusd endpoint' 'TUSD'
-readarray -t TUS_OPTIONS <<<"$(tus_options)"
-if [ "${OPT_OPTIONS}" -eq 1 ]; then
-  echo -e "\033[1;34m➤ ${TUSD} ☁\033[0m\n\033[2m⌄\033[22m"
-  if [ -z "${TUS_OPTIONS[*]}" ]; then
+if [ $OPT_DEBUG = 1 ]; then
+  set -x
+fi
+
+[ -z "$TUSD" ] && error 'tusd endpoint' 'TUSD'
+if ! tus_options="$(get_tus_options)"; then
+  echo "error: failed to get TUS options:"
+  echo "$tus_options"
+  exit 1
+fi
+readarray -t TUS_OPTIONS <<<"$tus_options"
+if [ "$OPT_OPTIONS" = 1 ]; then
+  echo -e "\033[1;34m➤ $TUSD ☁\033[0m\n\033[2m⌄\033[0m"
+  if [ ${#TUS_OPTIONS[@]} = 0 ]; then
     error "No tusd headers"
   else for opt in "${TUS_OPTIONS[@]}"; do
-    IFS=':' read -r -a header <<< "${opt}"
-    echo -e "\033[0;32m➤\033[0m ${header[0]}"
-    IFS=',' read -r -a values <<< "${header[1]}"
+    IFS=':' read -r key values <<< "$opt"
+    echo -e "\033[0;32m➤\033[0m $key"
+    if [ "${values:0:1}" = " " ]; then values="${values:1}"; fi
+    IFS=',' read -r -a values <<< "$values"
     for value in "${values[@]}"; do
-      echo -e "\033[2m↳ $(echo "${value}" | xargs)\033[22m"
+      echo -e "\033[2m  ↳ $(echo "$value" | xargs)\033[0m"
     done
   done; fi
   exit 0
@@ -281,71 +306,78 @@ fi
 
 tus_supports "creation" "Tusd can not perform file creation"
 
-[ ! -f "${1}" ] && usage 'No file given'
-FILE="${1}"
-SIZE="$(wc -c <"${FILE}")"
+[ ! -f "$1" ] && usage 'No file given'
+FILE="$1"
+SIZE="$(wc -c <"$FILE")"
 
-[ "${OPT_RESET}" -eq 1 ] \
-  && rm "${FILE}.tus" &>/dev/null || true
+if [ "$OPT_RESET" = 1 ]; then
+  rm "$FILE.tus" &>/dev/null
+fi
 
 declare -A Location
 # shellcheck source=/dev/null
-[ -f "${FILE}.tus" ] \
-  && . <(cat "${FILE}.tus" | grep -E '^(TUSD|TUS_HEADERS|TUS_CHUNK_SIZE|TUS_PARALLEL|Location)')
+if [ -f "$FILE.tus" ]; then
+  source <(grep -E '^(TUSD|TUS_HEADERS|TUS_CHUNK_SIZE|TUS_PARALLEL|Location)=' "$FILE.tus")
+fi
 # TODO vaildate values.
 
-total_parts="$(ceil "${SIZE}" "${TUS_CHUNK_SIZE}")"
+total_parts="$(ceildiv "$SIZE" "$TUS_CHUNK_SIZE")"
 
-if [ -z "${Location[@]}" ]; then
+if [ ${#Location[@]} = 0 ]; then
   headers=()
-  [ "${TUS_PARALLEL}" -gt 1 ] \
-    && headers+=("Upload-Concat: partial")
+  if [ "$TUS_PARALLEL" -gt 1 ]; then
+    headers+=("Upload-Concat: partial")
+  fi
 
   parts_per_partial=$((total_parts / TUS_PARALLEL))
-  for i in $(seq ${TUS_PARALLEL}); do
-    partials="${parts_per_partial}"
-    if [ "${i}" -eq "${TUS_PARALLEL}" ]; then
+  for i in $(seq "$TUS_PARALLEL"); do
+    partials="$parts_per_partial"
+    if [ "$i" = "$TUS_PARALLEL" ]; then
       partials=$(( partials + total_parts - i * parts_per_partial ))
       length=$(( SIZE - ( TUS_PARALLEL - 1 ) * parts_per_partial * TUS_CHUNK_SIZE ))
     else
       length=$(( partials * TUS_CHUNK_SIZE ))
     fi
 
-    tus_create "${FILE}" "${length}" "${headers[@]}" || error 'Tus file creation failed'
-    read dest < $tus_location
-    Location[$dest]="${partials}-${i}"
+    if ! dest="$(tus_create "$FILE" "$length" "${headers[@]}")"; then
+      error 'Tus file creation failed'
+    fi
+    # FIXME handle empty destinations
+    # if [ -z "$dest" ]; then
+    Location[$dest]="$partials-$i"
   done
 
   # create resumable log file
-  cat <<-EOTUS > "${FILE}.tus"
+  cat <<-EOTUS > "$FILE.tus"
 # settings
-TUSD="${TUSD}"
+TUSD="$TUSD"
 TUS_HEADERS="$(join ', ' "${TUS_HEADERS[@]}")"
-TUS_CHUNK_SIZE="${TUS_CHUNK_SIZE}"
-TUS_PARALLEL="${TUS_PARALLEL}"
+TUS_CHUNK_SIZE="$TUS_CHUNK_SIZE"
+TUS_PARALLEL="$TUS_PARALLEL"
 # tus parts
 $(declare -p Location)
-# ∑ ${total_parts} parts to upload.
+# ∑ $total_parts parts to upload.
 EOTUS
 fi
 
-echo -e "\033[0;35m∑\033[0m \033[1m${total_parts} parts\033[21m to upload."
+echo -e "\033[0;35m∑\033[0m \033[1m$total_parts parts\033[0m to upload."
 for dest in "${!Location[@]}"; do
-  __=(${Location[$dest]//-/ })
-  tus_upload "${dest}" "${FILE}" "${SIZE}" "${__[0]}" "${__[1]}" &
-  pids[$dest]=${!}
+  read parts multi <<<"${Location[$dest]//-/ }"
+  tus_upload "$dest" "$FILE" "$SIZE" "$parts" "$multi" &
+  pids[$dest]=$!
 done
 
 while [ ${#pids[@]} -gt 0 ]; do
   for dest in "${!Location[@]}"; do
     [ -e "/proc/${pids[$dest]}" ] && continue
-    unset pids[$dest]
+    unset "pids[$dest]"
   done
   sleep 1
 done
 
-if [ "${TUS_PARALLEL}" -gt 1 ]; then
-  tus_concat "${!Location[@]}" || error 'Tus concatenation failed'
-  read dest < $tus_location
+if [ "$TUS_PARALLEL" -gt 1 ]; then
+  if ! dest="$(tus_concat "${!Location[@]}")"; then
+    error 'Tus concatenation failed'
+  fi
 fi
-tus_done "${dest}"
+tus_done "$dest"