skypjack skypjack - 2 months ago 12
C Question

uv_fs_open: flags and mode on Windows

From the official documentation we have the following signature for


int uv_fs_open(uv_loop_t* loop, uv_fs_t* req, const char* path, int flags, int mode, uv_fs_cb cb);

And it is said that it is equivalent to

From the most accredited tutorial I've found on the web, we have this (emphasis mine):

flags and mode are standard Unix flags. libuv takes care of converting to the appropriate Windows flags.

Because of that, I thought that the following statement would have worked both on Linux and Windows:

uv_fs_open(my_loop, my_req, my_filename, O_RDWR | O_CREAT, S_IRWXU, my_callback);

Actually, it works just fine on Linux.

Anyway, on Windows I receive the following errors:

'O_RDWR': undeclared identifier

'O_CREAT': undeclared identifier

'S_IRWXU': undeclared identifier

Is it the expected result (and thus the tutorial is wrong)?

What should I do to have a call to
that just works on both the platforms?

What are the values for flags and mode to be used on Windows?


To be able to use uv_fs_open on Windows, users have to:

  • include fcntl.h explicitly, because uv-win.h doesn't include it (see this issue for further details)

  • use _O_CREAT, _O_RDWR_ and so on instead of O_CREAT, O_RDWR and the others (see the official documentation for further details)

Something similar applies to the mode and details on the available constants can be found in the linked documentation.