On Tue, 20 Jul 2004, Robert Locke wrote: > I'm not sure about the php code being referred to, but a more generic > problem for my understanding.... > > How does one have a line without an end to the line? I always assumed > that all lines ended with <LF>, including the last line of the file.... > I can conjecture the creation of text at the end of the file without a > <LF> at their end, but that to me is not really a line. I guess I fall > back to more of a read loop, I suppose.... > > Of course, this is the beauty of Unix/Linux: we can each define as we > see fit..... > > --Rob In Unix, there are no line-oriented files. Lines are a human construct for imposing order on what would otherwise appear to be chaos. Unix has record-oriented files (not an issue here) and stream-oriented files. Stream-oriented files appear to the filesystem as a single, unbroken string of characters, some of which may be '^J' (newline/linefeed). Many (most) programming languages have routines that will read the stream until the next '^J', so that programmers can think "naturally" in terms of lines, but this should not be construed as making the files line oriented. So a stream file can end with any character. In order to make these stream files fit with a line-oriented world view, many (most) text editors enforce that all lines--including the last one--end with '^J'. Some editors will allow this restriction to be overridden, and some programs will break on inputs created by those editors. When a program reads stream files, Unix will return characters until either it is told to stop or it attempts to read beyond the end of the file. A program that calls read routines that return the string of characters ending at the next newline will behave differently if the last line does not end with a newline. If the last newline is present, the program will read the last line without getting an end-of-file indication, and will only fail on the next read. If the last newline is missing, the program will get the end-of-file indication when it reads the last line. This can cause "fencepost" errors such as the one the OP had in his PHP snippet. -- Matthew Saltzman Clemson University Math Sciences mjs AT clemson DOT edu http://www.math.clemson.edu/~mjs
