How to call a Linux executable within an Asssember program.

Calling a Linux command from within an Assembler program is very easy. This example calls /bin/ps from within an Assembler program. This is a very neat trick.

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section .data
    cmd db '/bin/ps', 0
 
section .text
    global _start
 
_start:
    ; Execute the "ls" command
    mov eax, 11        ; System call number for execve
    mov ebx, cmd       ; Address of the command string
    xor ecx, ecx       ; No command line arguments
    xor edx, edx       ; No environment variables
    int 0x80
 
    ; Exit the program
    mov eax, 1
    xor ebx, ebx
    int 0x80

To assemble and run this program on Linux, you can follow these steps:

1. Save the code in a file named ls.asm.
2. Assemble the code using NASM assembler: nasm -f elf32 ls.asm -o ls.o.
3. Link the object file to create an executable: ld -m elf_i386 ls.o -o psme.
4. Run the program: ./psme.

This is the output you will get from this program.

┗━━━━━━━━━━┓ john@localhost ~/Documents
           ┗━━━━━━━━━━━━━╾ ╍▷ ./lsme 
    PID TTY          TIME CMD
   5926 pts/0    00:00:00 bash
  78883 pts/0    00:00:00 ps

This is a simple way to call a Linux command in asm. This might be a very useful programming tip.