QR factorization question

[jschenxiaoyu]

I am a totally new beginner using LAPACK and have some questions on QR factorization.
I want to achieve this function qr(A, 0) of matlab in my C code. Here A is a tall matrix. How can I achieve this by calling LAPACK GEQRF function to calculate QR factorization of A?
And I don't know how to call the function of LAPACK in C. Do I need to declare the LAPACK_SGEQRF function first in my code?
Thank you very much and I am really confused about how to implement the QR factorization in C.