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The make (UNIX) utility

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• The Make utility
  • The Make utility:

    Make application = a program that reads in the file dependencies in a Make file and execute the maintenance commands when the target file is out-of-date

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  • How to use the Make application:

    Write a Make file specifying the file dependencies and the maintenance commands for each target file that you need to maintain. Issue the following Make command to refresh the target file: make targetName

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  • Default Make target:

    If you run the make command without specifying a target name, then the make command will use the first target name in the Make file

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• Sample file dependencies and maintenance commands used in the demo
  • The demo files are stored in /home/cs255001/demo/C/Make/1

  • The file dependencies of this simple C project (consisting of one C program file) is:

    Source file: hello.c <==== source file | | gcc -c hello.c | V Object file: hello.o | | gcc -o hello hello.o | V Executable: hello <==== end product

  • The Make file that describes the file dependencies and the maintenance commands is:

    hello: hello.o # Meaning: target hello depends of hello.o <TAB> gcc -o hello hello.o # Command to update the target hello hello.o: hello.c # Meaning: target hello.o depends of hello.c <TAB> gcc -c hello.c # Command to update the target hello.o

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  • Example Program: (Demo above code)                                                
    • Prog files: /home/cs255001/demo/C/Make/1/*

    How to run the program:

    Demo:   make TARGET          Watch what commands will be executed

  • Result:

    If you want to make the target hello.o, execute this command: UNIX>> make hello.o gcc -c hello.c and the make utility creates the target hello.o Now, run make hello.o again, and you will see: UNIX>> make `hello.o' is up to date. The make utility has determined that hello.o is up-to-date !!! (The timestamp of hello.o is more recent than the source file hello.c and make skips the maintenance commands !!!) Next, remove hello.o and type make hello: UNIX>> make hello gcc -c hello.c gcc -o hello hello.o The make utility will first make hello.o and then it will use hello.o to make hello !!!

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  • Default make target illustrated:

    Typing make without any target: make will cause make to make the first target in the make file which is: hello: hello.o So it's the same as typing: make hello in the above example.

    For this reason, the first target is usually the end product program of the C project