CODEWITHSUNDEEP
cmakefilecompilation
antigravityguy
antigravityguy

Reputation: 157

Using "make" C Programming (Learn C the Hard Way)



I'm learning C Programming through "Learn C the Hard Way." I have am currently on Exercise 1, which can be found here: http://c.learncodethehardway.org/book/ex1.html

I understand the concept being covered, but don't understand the compiling process. While using the "make" command in the command line, why does this work:

$ make ex1

And this not work:

$ make ex1.c

I was actually just running the second command until a minute ago. I eventually figured it out though. Until I did, I kept getting this error message:

make: nothing to be done for 'ex1.c'

While this is a just a technicality, I would still like to know what's happening. Thanks :)

Upvotes: 7

Views: 2432

Answers (3)

user2958085
user2958085

Reputation: 11

the argument to the make tool is the name of the executable file that it will help create for you. It should not have a .c extension. You should have written make ex1 only.

Upvotes: 1

Jonathan Leffler
Jonathan Leffler

Reputation: 753455

Both work; they just do different tasks.

  • make ex1.c says "using the rules in the makefile plus built-in knowledge, ensure that the file ex1.c is up to date".

    The make program finds ex1.c and has no rules to build it from something else (no RCS or SCCS source code, for example), so it report 'Nothing to be done'.

  • make ex1 says "using the rules in the makefile plus built-in knowledge, ensure that the file ex1 is up to date".

    The make program finds that it knows a way to create an executable ex1 from the source file ex1.c, so it ensures that the source file ex1.c is up to date (it exists, so it is up to date), and then makes sure the ex1 is up to date too (which means 'file ex1 was modified more recently than ex1.c). If you've edited ex1.c since you last ran make, it will do the compilation to make ex1 newer than ex1.c. If the compilation fails, the file ex1 won't exist, so you'll get another recompilation next time too. And once it is up to date, then make won't rebuild ex1 again until you modify the source again.

This is the way make is designed to work.

Upvotes: 12

aschepler
aschepler

Reputation: 72271

The target to make usually specifies what you want it to build or rebuild, not what you want it to use to build something else.

If you type ex1.c (and there's no rule to auto-generate it), make essentially just answers "Yup, that file exists."

Upvotes: 4

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