Mingw32, unistd.h and my program

[Al-Burak]

I have a class that uses unistd.h functions for file I/O handling, I
have not used this class in a long time, but it worked just fine in
LINUX and CYGWIN, but under MINGW32 it doesn't even recognize the
function in unistd.h, and the compiler gives me errors like.

gnu_io.cpp:10: error: `F_OK' undeclared (first use this function)
gnu_io.cpp:10: error: `access' undeclared (first use this function)

What am I doing wrong?