12.04 Assembling and linking the assembly file

Step 1 will be assembling the file we created in 12.03 Writing assembly part 1.

Assembling the assembly file

Info

If you haven’t installed NASM yet, you can find the instructions here

Open up your terminal again and run the following command:

nasm -f elf64 test.asm

elf64 is the architecture of linux we are using (you can also write -felf64) test.asm is the assembly file you just wrote.

If everything went right, the file test.o should have appeared. This is an object file. If you open it up in a hex editor, you can read trough it, though its quite empty

After this, even though we haven’t used any external libraries, we are going to run the linker to turn this into an executable.

Linking the object file into an executable

Open up your command terminal again and run the following command:

ld test.o -o test

ld is the linker command, test.o is the target object file, and -o test is the output executable.

Running the executable

If you want to see the returned exit code, just running isnt enough. You need to run two commands to execute, and see the output of your program. Firstly, run:

./test

If everything went well, nothing should happen. Now run:

echo $?

If everything went right up to this point, you should see a 0 in the output of your command line.

Congrats, you made your first program in assembly!