what is the usage of $(if) in makefile?

In Makefile, $(if) is a conditional function that allows you to test if a condition is true or false. It has the following syntax:

$(if condition,then-part[,else-part])

If the condition is true, the function returns the then-part, otherwise, it returns the else-part. The else-part is optional and can be omitted.

Here's an example of how to use $(if) in a Makefile:

ifeq ($(DEBUG), true)
CFLAGS = -g -Wall
else
CFLAGS = -O2
endif

$(CC) $(CFLAGS) -o program program.c

In this example, the $(if) function is not used directly, but the ifeq directive is used to test the condition $(DEBUG) which is either true or false. If it's true, the CFLAGS variable is set to include debugging symbols and warnings, otherwise, it's set to optimize the code. The resulting CFLAGS value is then used to compile the program.c file.