A Little History on 0D0A

http://www.perlmonks.org/index.pl?node_id=68687

in reply to Cross platform file I/O code As Trimbach said, you should not have a problem. But why is there such a concern with the compatiliblity between record seperators across platforms in the first place? Why so much trouble? Time for a little history: Blame it on the typewriters - better yet, that lever or button on the right side of them. The one used to start typing on the next line. When you activate it, it causes the carriage to 'return' to the right so the hammers are lined up on the left side of the paper (carriage return) the carriage to roll up so the hammers are lined up on the next 'line' down (line feed) In the early 1900's teletypwriters were used to relay messages. Teletypwriters were descendants of the telegraph, and used a code similar to ASCII, called Baudot (or Murray) code. An operator could type into the teletypewriter (tty for short) and print a message on another tty far away.In this Baudot code, two special characters were designated for a Carriage Return(0x02) and a Line Feed(0x08). Baudot code went the way of the dinosaur for reasons outside the scope of this discussion, but the CR and LF characters were adopted by ASCII with different values: CR = 0x0D = \015 = \r LF = 0x0A = \012 = \n [download] Why were they adopted? For printers of course. The concept of the tty was split into two - a monitor and a printer. At this point, it was up to the various operating systems to implement their actual use. Oops. Macintosh: \r Windows : \r\n Unix : \n [download] UPDATE: Disregard that last table, kept only for historical purposes. Here is a better table, one that shows how the three different operatiing systems interpret a logical newline (ps, thanks Mr. Stein =] ) Unix : \n = \012 Macintosh: \n = \015 Windows : \n = \012 if handled as ASCII Windows : \n = \015\012 if handled as binary [download] This only causes problems when you transfer ASCII files around different operating systems as binary data, in which case you should use binmode - or when you are programming with sockets, in which case you will need to set $/ to '\015\012' or just use the exported globals $CRLF and CRLF() from the Socket or IO::Socketmodules.So, the next time you find yourself cursing this confusion, just take a look at this typewriter history tree and remember that we are only human, except arhuman. :) Jeff R-R-R--R-R-R--R-R-R--R-R-R--R-R-R-- L-L--L-L--L-L--L-L--L-L--L-L--L-L-- UPDATE: Thanks to the anonymous monk for clarifying things up.REFERENCES: Netword Programming With Perl by Lincoln D. Stein Code by Charles Petzold