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

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I'm learning C Programming through "Learn C the Hard Way." I have am currently on Exercise 1, which can be found here:

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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 :)

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."

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.

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.