[Question] What will happen if I subscribe fd in redisContext with EPOLLIN?

[w1nda]

The code link:

hiredis/hiredis.h

Line 262 in e0f4820

redisFD fd;

Thanks for attention,
My understanding is that EPOLLIN means when the associated file(fd) is available for read it will notify subscriber.

If I subscribe fd in redisContext with EPOLLIN, when I will got notified?
Or, put it in another way, what the fd means in redisContext? can I communicate with redis server with that fd(socket?)?
Or, put it in another way, when the socket is not ready for read?

[michael-grunder]

On Linux (or Linux-like) systems, redisFD is just a plain integer file descriptor. The reason there is an abstraction is to handle Windows.

hiredis/hiredis.h

Lines 173 to 183 in e0f4820

	#ifndef _WIN32
	typedef int redisFD;
	#define REDIS_INVALID_FD -1
	#else
	#ifdef _WIN64
	typedef unsigned long long redisFD; /* SOCKET = 64-bit UINT_PTR */
	#else
	typedef unsigned long redisFD; /* SOCKET = 32-bit UINT_PTR */
	#endif
	#define REDIS_INVALID_FD ((redisFD)(~0)) /* INVALID_SOCKET */
	#endif

You can use any of the common functions to operate against file descriptors. It's important to be careful if you manually poll/read/write to the fd while the redisContext owns it, but this is perfectly doable.