Undeclared first use of function

I get an undeclared first use of function on this line of code if ( fcntl( desc, F_SETFL, FNDELAY ) =bailout= -1 ) to do with bailout, how or where do i go about declaring it so i can get it to compile.

is that an exact copy of the code? If so is not like to work at all. If thats not an exact copy, you'll probably have to either post a copy of the error, or a copy of the code ( both would be better ). If your asking something else entirely different, you may need to clarify, cause your post is kind of confusing me.

EDIT

If your having a problem with fcntl, then you may need to include fcntl.h at the top of your file with the other includes.