CODEWITHSUNDEEP
c++windowscommand-linenewlinehttp-redirect
user594561
user594561

Reputation: 63

c++ newline character under windows command line redirection

I found that Windows command line redirection will replace '\n' with '\r\n' automatically. Is there any method to avoid this situation? Because after stdout or stderr redirection, you will got '\r\r\n' instead of '\r\n' if you write '\r\n' to the console.

Thanks a lot!

you can just try a simple program:

fprintf(stdout,"Hello, world!\r\n");

then you run it with redirection:

demo 1>demo.log

By using any HEX editor, you will find that '\r\n' is represented by '\r\r\n'.

UPDATE:

@steve-jessop I have solved this problem by using setmode, which will force stdout using O_BINARY mode. So the stream won't translate \n into \r\n.

Thanks a lot!

Upvotes: 3

Views: 6103

Answers (2)

Martin Green
Martin Green

Reputation: 1054

'\n' is the platform-independent newline representation. It's expanded by the compiler to whatever is the actual newline representation for the platform you're compiling for -- '\r\n' for Windows, and '\n' for *nix and friends, including MacOS.

So this is why you see '\r\r\n' in hex editor -- '\n' from '\r\n' that you wrote in source was expanded to '\r\r\n'.

Upvotes: 6

Steve Jessop
Steve Jessop

Reputation: 279245

The way to avoid it is to not write "Hello, world!\r\n". Either fprintf(stdout,"Hello, world!\n"); or std::cout << "Hello, world!" << std::endl; is sufficient.

This isn't particular to command-line redirection or stdout, the same would be true with any file descriptor open in character mode (as opposed to binary mode).

Upvotes: 7

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