Question

I’m trying to analyse some code (not written by myself) which calls readlink with a positive bufsize, and then tests if the result is zero. I can’t see how the result can be zero, with everything I’ve tried it is either -1, size of the real link or size of the soft link.

Can the result be zero, and if so how?

Answer 1

The POSIX description of readlink() says:

RETURN VALUE
Upon successful completion, readlink() shall return the count of bytes placed in the buffer. Otherwise, it shall return a value of -1, leave the buffer unchanged, and set errno to indicate the error.

Since the empty string is not a valid file name, I can see no way that the return value will be zero if the bufsize is bigger than 0.