make: Nothing to be done for `all'

Question

I am going through an eg pgm to create a make file.

http://mrbook.org/tutorials/make/

My folder eg_make_creation contains the following files,

Answer 1

That is not an error; the make command in unix works based on the timestamps. I.e let's say if you have made certain changes to factorial.cpp and compile using make then make shows the information that only the cc -o factorial.cpp command is executed. Next time if you execute the same command i.e make without making any changes to any file with .cpp extension the compiler says that the output file is up to date. The compiler gives this information until we make certain changes to any file.cpp.

The advantage of the makefile is that it reduces the recompiling time by compiling the only files that are modified and by using the object (.o) files of the unmodified files directly.