My handwritten C++ Makefile gives command not found

Question

I made a makefile to help compile multiple C++ files, but it is giving me "command not found" errors. I need to fix it.

The errors I get:

Make: line 1: main.out::command not found 
g++: error: GradeBook.o: No such file or directory 
g++: error: main.o: No such file or directory 
g++: fatal error: no input files 
compilation terminated. 
Make: line 4: main.o:: command not found 
Make: line 7: GradeBook.o:: command not found 
Make: line 10: clear:: command not found 

Here is my makefile:

main.out: GradeBook.o main.o
    g++ -Wall -g -o main.out GradeBook.o main.o 

main.o: main.cpp GradeBook.h
    g++ -Wall -g -c main.cpp

GradeBook.o: GradeBook.cpp GradeBook.h
    g++ -Wall -g -c GradeBook.cpp

clean:
    rm -f main.out main.o GradeBook.o 

Answer 1

Here's a list of typical mistakes people make with makefiles.

Issue #1 - using spaces instead of tabs

The command make is notoriously picky about the formatting in a Makefile. You'll want to make sure that the action associated with a given target is prefixed by a tab and not spaces.

That is a single Tab followed by the command you want to run for a given target.

Example

This being your target.

main.out: GradeBook.o main.o

The command that follows should have a single Tab in front of it.

    g++ -Wall -g -o main.out GradeBook.o main.o 
^^^^--Tab

Here is your Makefile cleaned up

//Here is my makefile:

main.out: GradeBook.o main.o
        g++ -Wall -g -o main.out GradeBook.o main.o 

main.o: main.cpp GradeBook.h
        g++ -Wall -g -c main.cpp

GradeBook.o: GradeBook.cpp GradeBook.h
        g++ -Wall -g -c GradeBook.cpp

clean:
        rm -f main.out main.o GradeBook.o 

Issue #2 - naming it wrong

The tool make is expecting the file to be called Makefile. Anything else, you need to tell make what file you want it to use.

$ make -f mafile

-or- 

$ make --file=makefile

-or-

$ make -f smurfy_makefile

NOTE: If you name your file Makefile, then you can get away with just running the command:

$ make

Issue #3 - Running Makefiles

Makefile's are data files to the command make. They aren't executables.

Example

make it executable

$ chmod +x makefile

run it

$ ./makefile 
./makefile: line 1: main.out:: command not found
g++: error: GradeBook.o: No such file or directory
g++: error: main.o: No such file or directory
g++: fatal error: no input files
compilation terminated.
./makefile: line 4: main.o:: command not found
g++: error: main.cpp: No such file or directory
g++: fatal error: no input files
compilation terminated.
./makefile: line 7: GradeBook.o:: command not found
g++: error: GradeBook.cpp: No such file or directory
g++: fatal error: no input files
compilation terminated.
./makefile: line 10: clean:: command not found

Other isues

Beyond the above tips I'd also advice you to make heavy use of make's ability to do "dry-runs" or "test mode". The switches:

   -n, --just-print, --dry-run, --recon
        Print the commands that would be executed, but do not execute them 
        (except in certain circumstances).

Example

Running the file makefile.

$ make -n -f makefile 
g++ -Wall -g -c GradeBook.cpp
g++ -Wall -g -c main.cpp
g++ -Wall -g -o main.out GradeBook.o main.o 

But notice that none of the resulting files were actually created when we ran this:

$ ls -l
total 4
-rw-rw-r--. 1 saml saml   0 Dec 22 08:39 GradeBook.cpp
-rw-rw-r--. 1 saml saml   0 Dec 22 08:45 GradeBook.h
-rw-rw-r--. 1 saml saml   0 Dec 22 08:45 main.cpp
-rwxrwxr-x. 1 saml saml 262 Dec 22 08:25 makefile

Answer 2

From the error messages, it appears you're running your Makefile as if it was an executable or shell script (i.e. you've set the executable bit and run ./Make).

That's not how its done. You need to invoke make to run your Makefile, i.e.:

$ make -f Make

Or if you rename your file to Makefile, you can simply type:

$ make