What does '<<' mean in C?

Question

what does this mean?

#define WS_RECURSIVE    (1 << 0)

I understand that it will define WS_Recursive (1 << 0) but w

Answer 1

<< computes a bitwise shift to the left. Shifting 1 to the left by 0 bits simply leaves the result as 1.

I noticed also where you got your code from that there's also:

#define WS_RECURSIVE    (1 << 0)
#define WS_DEFAULT  WS_RECURSIVE
#define WS_FOLLOWLINK   (1 << 1)
#define WS_DOTFILES     (1 << 2)
#define WS_MATCHDIRS    (1 << 3)

That is a way of creating bit fields, where you OR (|) flags together, and AND them (&) to check if they're set.