Why this simple program leads to different carriage return/line feed file when executed in Java and AIX?

Question

If I run this simple program on Windows 7 and then on AIX (Unix system) and compare the two generated files using a tool such as Winmerge or Compare It, it tells me that the Carriage Return and Line Feed are different but the content identical.

Why is that? Isn't supposed to be the same if both use the same encoding "UTF-8" in this case?
How can I make both files totally equal?

public class WriteFile {

    public static void main(String[] args) throws IOException {
        write();

    }

    public static void write() throws IOException {
        File file = new File("/tmp/test.txt");
        file.delete();
        file.createNewFile();
        String str = "hello";
        FileOutputStream fileOs = new FileOutputStream(file);
        PrintWriter writer = new PrintWriter(new OutputStreamWriter(fileOs, "UTF-8"), true);
        writer.println(str);
        writer.close();
    }

}

Not 100% sure but UTF-8 is only an encoding, I think linefeeds/returns are left up to the OS. — Andrew White, Oct 13 '11 at 15:48
UTF-8 describes how the characters are encoded, not what characters are written to the file. — unholysampler, Oct 13 '11 at 15:49

NPE · Accepted Answer · 2011-10-13T16:13:54.610

5

Different operating systems use different newline conventions:

On Windows, newlines are CR+LF;
On Unix, newlines are LF.

(If you're curious, there's more.).

If you need the output files to be identical, don't use println(), but write \n or \r\n instead:

writer.printf("%s\n", str);   // LF
writer.printf("%s\r\n", str); // CR+LF

edited Oct 13 '11 at 16:13

answered Oct 13 '11 at 15:47

NPE

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Thank you. It worked. So calling writer.println is platform dependent. Also if I want to use CR+LF I can also use writer.printf("%s\r\n", str). – Alfredo Osorio Oct 13 '11 at 16:01
`println` is platform-dependent, yes, *by design*. The idea is it will always work correctly for the platform you're on. But if you need identical outputs from different platforms, then you have to pick which rule you want to follow. – Dan Oct 13 '11 at 16:11
@AlfredoO: Yes, `\r\n` will give CR+LF. – NPE Oct 13 '11 at 16:13

score 3 · Answer 2 · answered Oct 13 '11 at 15:47

3

Use

writer.print(str + "\n");

instead of

writer.println(str);

answered Oct 13 '11 at 15:47

stivlo

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score 1 · Answer 3 · answered Oct 13 '11 at 16:12

Like it's been said, you should switch from using println(String) to print(String) or printf(String, ...)

Check out the documentation for println(String) (emphasis mine):

Prints a String and then terminates the line. This method behaves as though it invokes print(String) and then println().

And the docs for println():

Terminates the current line by writing the line separator string. The line separator string is defined by the system property line.separator, and is not necessarily a single newline character ('\n').

You can read about the line.separator system property here.

I would go with aix's suggestion of using

writer.printf("%s\n", str);

Why this simple program leads to different carriage return/line feed file when executed in Java and AIX?

3 Answers3

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