Flatten multiple tar files in to a single tar file

sr

#!/usr/bin/env bash



set -e

declare entrypoint="" ; entrypoint=$( readlink -f "${BASH_SOURCE[0]}" 2>/dev/null || echo "$0" )

sr_steam_roller() {

  local output_mode=$1
  local output_file=""

  local input_files=("${@:2}")

  case $output_mode in
    -) output_file="/dev/stdout" ;;
    =) output_file=$(mktemp) ;;
    *) output_file=$output_mode ;;
  esac

  for input_file in "${input_files[@]}"; do

    [[ $input_file = "-" ]] && input_file="/dev/stdin"

    tar --extract \
      --file "$input_file" \
      --ignore-zeros \
      --totals \
      --to-command="TAR_OUTPUT_FILE=$output_file ; source $entrypoint ; sr_update_file"

  done

  if [[ $output_mode = "=" ]]; then 
    cat "$output_file"
    rm -f "$output_file"
  fi

}

sr_update_file() {

  local temp_file="" ; temp_file=$( mktemp )

  cat > "$temp_file"

  tar --append \
    --file "$TAR_OUTPUT_FILE" \
    --mode="$TAR_MODE" \
    --transform="s|.*|$TAR_FILENAME|" \
    --owner="$TAR_UNAME" \
    --group="$TAR_GNAME" \
    --mtime="$(date -d @"$TAR_MTIME")" \
    --dereference "$temp_file"

  rm "$temp_file"

}

sr_main() {

  if [[ $1 = "--help" ]]; then

    printf '%s\n'\
      'sr - steam-roller - Flatten multiple tar archives in to a single (non concatenated) archive ' \
      '                                                                                            ' \
      'Usage:                                                                                      ' \
      '  sr --help                                                                                 ' \
      '  sr <(output_file> | - | = )> [( - | input_files...)]                                      ' \
      '                                                                                            ' \
      'Ouput target:                                                                               ' \
      ' - : Output resulting tar file to stdout                                                    ' \
      ' = : Generate a temp file to write to and write that to stdout when done                    ' \
      ' output_file : Append directly to specified tar file (or create if it doesn''t exist)       ' \
      '                                                                                            ' \
      'Examples:                                                                                   ' \
      '  Concatenate all tar files, flatten using sr and output to file                            ' \
      '    cat ./*.tar | sr - - > ./output.tar                                                     ' \
      '                                                                                            ' \
      '  Same as above with all the filenames provided                                             ' \
      '    sr ./output.tar ./*.tar                                                                 '

    exit

  fi

  sr_steam_roller "$@"

}

export -f sr_update_file

(return 0 2>/dev/null) || sr_main "$@"