######################################################################
# USAGE: CreateHexFile FILENAME [LIST]
# This function creates a binary file and writes some bytes in it.
# The first argument should be the full name of the file to be
# created. The following arguments must be pairs of hexadecimal
# digits which are converted to bytes and written to the file.
# Finally, the function creates a global variable named $SUCCESS
# and will write the number of bytes written into this variable.
# If an error occurs, then this variable will hold an empty string.
# If the function was called with only one argument, meaning that
# no bytes were expected to be written, then the function will
# create a file and leave it blank, and $SUCCESS will be set to 0.
#
# Example:
#
#     CreateHexFile "myfile.tmp"  00 c3 9d 80 7e 92 23 ff 00 2c
#     if [[ $SUCCESS ]]; then
#       echo "$SUCCESS bytes written successfully."
#     else
#       echo "Failed to create file."
#     fi
#
function CreateHexFile
{
  SUCCESS=''
  local filename="$1"
  local bytecount=0
  local byte
  local hex
  shift

  # Create the file
  > "$filename"

  # File exists?
  if [[ -f $filename ]]; then

    # Make sure file length is zero at this point:
    local filelen=$(stat --printf="%s" "$filename")
    if [[ $filelen -gt 0 ]]; then
      return 0
    fi

    SUCCESS=0

    # Convert hexadecimal numbers to bytes
    # and write them to the file:
    for hex in "$@"; do
      # Remove everything except hexadecimal digits
      hex=$(printf '%s' "${hex//[![:xdigit:]]}")
      for (( i=0; i<${#hex}; i+=2 )); do
        # Take two digits at a time
        byte="\\x${hex:i:2}"
        # Write it to the file one byte at a time
        printf "$byte" >> "$filename"
        # Count number of bytes sent to the file
        bytecount=$((bytecount + 1))
      done
    done

    if [[ $bytecount -gt 0 ]]; then
      local filelen=$(stat --printf="%s" "$filename")
      if [[ $filelen -eq $bytecount ]]; then
        SUCCESS=$filelen
      fi
    fi
  else
    echo "Error: Cannot create file - $filename" >&2
  fi
}

$MyList = " 00 01 02 03 04 05 06 07 "

CreateHexFile "ASCIIBASH.BIN" $MyList