What is the simplest way to write to stdout in binary mode?

Question

I've been trying to figure out the best way to write binary data to stdout from a C program. It works fine on Linux, but I'm having issues when I compile on Windows because "\n" gets converted to "\r\n".

Is there a standard way to write to stdout in some sort of binary mode which avoids newline conversion? If not, what is the simplest way to get Windows to stop doing this?

I'm using GCC and MinGW, and writing to stdout using fwrite.

Answer 1

You can use setmode(fileno(stdout), O_BINARY)

Wrap it in an ifdef if you want to keep it compatible with Linux.

See also: https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/setmode?view=vs-2017

Answer 2

You can do something like that (which is sort of cross platform):

FILE *const in = fdopen(dup(fileno(stdin)), "rb"); FILE *const out = fdopen(dup(fileno(stdout)), "wb"); /* ... */ fclose(in); fclose(out); 

Or you can use write() and read() system calls directly with fileno(stdin) and fileno(stdout). Those system calls operate on lower level and don't do any conversions. But they also don't have buffering that you get from FILE streams.