Some notes on Make</HEAD>

Some notes on using the UNIX make facility

To create an executable program which needs multiple files you may either

compile all the files together or
- Example: cc main.c myio_c.c array_int.c
- Drawbacks:
  1. all the .c files are recompiled whether they need to be or not
  2. you have to remember all the files (or create an alias)
- Benefits: easy to use
use the make facility to do it for you
- Example: make myprog
- Once the command make has been given, the make program actually compiles the program based on the "rules" you give it when you create the file to be used.
- If any .o file has an earlier date than its corresponding .c and/or .h file, it is recompiled. Otherwise, it is left alone; thus saving compile time.
- More difficult to use since you have to create a file for the make program to use. This file is usually called makefile or Makefile and is in the same directory with the files it is using. You may use any name you have to give that name to make.
- Example of a Makefile - The file is named Makefile and is in the same directory as the files indicated. To use this you would type make tester at the system prompt. If there are no compile errors, an executable file named tester is created. NOTE: the second line that starts with cc -o is TABBED in. You MUST use the TAB. Spaces won't work.
```
   tester :  main.o myio_c.o array_int.o
   	cc - o tester main.o myio_c.o array_int.o
   main.o : main.c
   myio_c.o : myio_c.c myio_c.h
   array_int.o : array_int.o array_int.h
```
- In the above example, the main.o : main.c could be omitted since make knows to use .c to produce a .o. However, since the others also need .h files, they must be included.
- If you want to name your Makefile something other than Makefile or makefile, you may use any name you wish; however, you must give this name to make since make by default looks for a makefile or a Makefile in your directory. For example, use
```
   %make -f MyMakeName tester
        
```
  Where tester is the target executable that you named in the makefile. The inclusion of tester is optional.