Newline conversion on reading?

Ruby
1

I can’t get newline conversions to work while reading:

File.write('foo.txt', "foo\r\nbar\r\n")
File.open('foo.txt', 'r', universal_newline: true) {|fh| fh.read}
# => "foo\r\nbar\r\n", no normalization performed

Are they only supposed to work for writing? If yes, why the asymmetry?

2

Xavier N. wrote in post #1082114:

I can’t get newline conversions to work while reading:

File.write('foo.txt', "foo\r\nbar\r\n")

If you are on a Window operating system, ruby will convert any “\n” in
your output to “\r\n” before actually writing to the file.
So lets look through your output and convert any
“\n” characters to “\r\n” to see what is actually written to the file.
This line:

foo\r…\n…bar…\r…\n

gets written as:

foo\r…\r\n…bar…\r…\r\n

…because there are two “\n” characters that ruby converts to “\r\n”.
It does not matter whether the “\n” is adjacent to a “\r” or not.

File.open('foo.txt', 'r', universal_newline: true) {|fh| fh.read}
# => "foo\r\nbar\r\n", no normalization performed

Are they only supposed to work for writing? If yes, why the asymmetry?

On Windows, the conversion that ruby performs when you read from a file
is to convert any “\r\n” it sees to “\n”, so this line in the file:

foo\r…\r\n…bar…\r…\r\n

gets handed to your ruby program as:

foo\r…\n…bar…\r…\n

Inside your ruby program, “\n” stands for whatever newline your system
uses. You should not attempt to use the actual newline for your
system in your output.

3

On Wed, Oct 31, 2012 at 3:08 AM, 7stud – [email protected] wrote:

Xavier N. wrote in post #1082114:

foo\r…\n…bar\r…\n

That test ran on a Mac.

If you try that on a Unix machine you’ll see :universal_newline is not
doing CRLF to LF conversion on reading.

4

Looking at the test suite for 1.9.3 I see you need to explicitly
enable textmode with either:

open(filename, 'rt')
open(filename, 'r', textmode: true)

That enables universal newline convention by default, though you can
disable it by passing universal_newline: false.