im making my own programming language and i wanted to call some functions from libc (es strcat and printf) but im unsure on how to call them correctly(i dont which cpu registry to use and if i have to actually use them to pass arguments), by now i got printf to work following a git hub example. (https://gist.github.com/jamichaels/a5e770105615d9e32b18)

This is how i ended up printing stuff:

SECTION .data
     endLine db 0Ah, 0
     integer_printf:     db  '%d',   10,0
     float_printf        db  '%f',   10,0
     string_format       db  '%s',   10,0
     var     db "test",0
SECTION .text
     extern printf
     global main
printInt:
     mov rdi,integer_printf
     xor rax,rax
     call printf
     ret
printFloat:
     mov rdi,float_printf
     call printf
     ret
printStr:
     mov rdi,string_format
     xor rax,rax
     call printf
     ret
exit_program:
     mov rax, 60
     syscall
main:
     mov rsi, var
     call printStr

     MOV rdi, 30
     call exit_program

nasm -f elf64 -o test.o main.asm && gcc -o test test.o -lc -no-pie

thanks in advice for any help