5.13.4 The Last Line of a Stream How to handle the last line in a stream is sometimes a problem. If you use a system that stores end-of-lines as special character sequences, and the last part of the data of a stream is an unterminated line, then what is returned when you try to read that part of data? There are three possible solutions: First, it may interpret the end-of-file itself as an implicit end-of-line, in this case, the partial part of the line is returned, as if it was properly terminated. Second, it may raise the NOTREADY condition, since the end-of-file was encountered during reading. Third, if there is any chance of additional data being appended, it may wait until such data are available. The second and third approaches are suitable for persistent and transient files, respectively. The first approach is sometimes encountered. It has some problems though. If the end of a stream contains the data ABC<NL>XYZ, then it might return the string XYZ as the last line of the stream. However, suppose the last line was an empty line, then the last part of the stream would be: ABC<NL>. Few would argue that there is any line in this stream after the line ABC. Thus, the decision whether the end-of-file is an implicit end-of-line depends on whether the would-be last line has zero length or not. An pragmatic solution is to let the end-of-file only be an implicit end-of-file if the characters immediately in front of it are not an explicit end-of-line character sequence. However, TRL gives some indications that an end-of-file is not an implicit end-of-line. It says that LINES() returns the number of complete lines left, and that LINEIN() returns a complete line. On the other hand, the end-of-line sequence is not rigidly defined by TRL, so an implementor is almost free to define end-of-line in just about any terms that are comfortable. Thus, the last line of a stream may be a source of problem if it is not explicitly terminated by an end-of-line.