[Israel.pm] newline character as a portability issue
Jason.Elbaum at freescale.com
Wed Jul 7 23:17:49 PDT 2004
Shlomo Yona wrote:
> LF eq \012 eq \x0A eq \cJ eq chr(10) eq ASCII 10
> CR eq \015 eq \x0D eq \cM eq chr(13) eq ASCII 13
This is correct in ASCII. Historical note from teleprinter days:
LF == "linefeed" which means "advance the paper one line"
CR == "carriage return" which means "move the print head back to the
So, technically speaking, to start a new print line you had to do both
(CRLF): Return to the leftmost column and advance one line.
Since this was redundant - every line ended with two characters - some
systems decided to treat LF as if it were a CRLF, and other systems
treated CR as CRLF.
That's why, by default, Unix ends lines with ASCII 10, Mac with ASCII
13, and DOS with 13-10.
Keep in mind, though, that not all systems use ASCII! Quoting perlport
> These are just the most common definitions of \n and \r in Perl. There may well be others. For example, on an EBCDIC implementation such as z/OS or OS/400 the above material is similar to "Unix" but the code numbers change:
> LF eq \025 eq \x15 eq chr(21) eq CP-1047 21
> LF eq \045 eq \x25 eq \cU eq chr(37) eq CP-0037 37
> CR eq \015 eq \x0D eq \cM eq chr(13) eq CP-1047 13
> CR eq \015 eq \x0D eq \cM eq chr(13) eq CP-0037 13
You're not likely to encounter EBCDIC systems in the wild these days,
but you do need to consider just how portable you want your code to be.
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