For the spirit of the LORD fills the world, all-embracing, and knows what man says. Wisdom 1:7 #if HAVE_SYS_WAIT_H # include <sys/wait.h> #endif Implication. If p then q. [math] { p \; \Rightarrow \; q } [/math] If HAVE_SYS_WAIT_H is true (nonzero value) then compile the following line(compilation of #include <sys/wait.h>) will be done. http://www.cprogramming.com/tutorial/cpreprocessor.html …