def push(bytes)
      if bytes.length != @entry_bytes
        PEROBS.log.fatal "All stack entries must be #{@entry_bytes} " +
          "long. This entry is #{bytes.length} bytes long."
      end
      begin
        @f.seek(0, IO::SEEK_END)
        @f.write(bytes)
      rescue => e
        PEROBS.log.fatal "Cannot push to stack file #{@file_name}: #{e.message}"
      end
    end
def push(bytes)
      if bytes.length != @entry_bytes
        PEROBS.log.fatal "All stack entries must be #{@entry_bytes} " +
          "long. This entry is #{bytes.length} bytes long."
      end
      begin
        @f.seek(0, IO::SEEK_END)
        @f.write(bytes)
      rescue => e
        PEROBS.log.fatal "Cannot push to stack file #{@file_name}: #{e.message}"
      end
    end
Push the given bytes onto the stack file.
 @param bytes [String] Bytes to write.