Title here
Summary here
Command Line Arguments in Assembly Language
section .data
argsWithProg db "Command line arguments with program name:", 0
argsWithoutProg db "Command line arguments without program name:", 0
argMsg db "Third argument:", 0
newline db 10
section .text
global _start
_start:
; Get the command line arguments
pop rax ; Get the number of arguments
mov rbx, rax ; Store the number of arguments in rbx
; Print argsWithProg message
mov rax, 1
mov rdi, 1
mov rsi, argsWithProg
mov rdx, 46
syscall
; Print all arguments (including program name)
mov rcx, rbx ; Set counter to number of arguments
print_loop:
pop rsi ; Get next argument
call print_string
loop print_loop
; Print newline
mov rax, 1
mov rdi, 1
mov rsi, newline
mov rdx, 1
syscall
; Print argsWithoutProg message
mov rax, 1
mov rdi, 1
mov rsi, argsWithoutProg
mov rdx, 51
syscall
; Print arguments without program name
dec rbx ; Decrease counter to skip program name
mov rcx, rbx
print_loop2:
pop rsi ; Get next argument
call print_string
loop print_loop2
; Print newline
mov rax, 1
mov rdi, 1
mov rsi, newline
mov rdx, 1
syscall
; Print third argument (if it exists)
cmp rbx, 3 ; Check if we have at least 3 arguments
jl exit ; If not, exit
mov rax, 1
mov rdi, 1
mov rsi, argMsg
mov rdx, 15
syscall
pop rsi ; Get program name (discard)
pop rsi ; Get first argument (discard)
pop rsi ; Get second argument (discard)
pop rsi ; Get third argument
call print_string
; Exit program
exit:
mov rax, 60
xor rdi, rdi
syscall
; Function to print a null-terminated string
print_string:
push rax
push rdi
push rdx
push rcx
mov rdx, 0
count_loop:
cmp byte [rsi + rdx], 0
je done_counting
inc rdx
jmp count_loop
done_counting:
mov rax, 1
mov rdi, 1
syscall
pop rcx
pop rdx
pop rdi
pop rax
retThis Assembly Language code demonstrates how to work with command-line arguments. Here’s an explanation of how it works:
The code starts by defining some constant strings in the
.datasection.In the
_startfunction, it first retrieves the number of command-line arguments.It then prints all arguments, including the program name, by looping through the argument list on the stack.
After that, it prints the arguments again, but this time skipping the program name.
Finally, if there are at least three arguments, it prints the third argument separately.
The
print_stringfunction is a utility to print null-terminated strings.
To assemble and link this program, you would typically use nasm and ld. For example:
$ nasm -f elf64 command_line_arguments.asm
$ ld -o command_line_arguments command_line_arguments.o
$ ./command_line_arguments arg1 arg2 arg3
Command line arguments with program name:./command_line_arguments arg1 arg2 arg3
Command line arguments without program name:arg1 arg2 arg3
Third argument:arg3Note that Assembly Language is much lower level than high-level languages, so this implementation is more verbose and requires manual memory management and system call invocations.