# pwd.S - simple assembler for Linux

#include <asm/unistd.h>
#include <linux/limits.h>     

/* Some constants */

#define KERNEL    0x80        
#define NEWLINE   '\n'
#define STDOUT    1
#define OK_EXIT   0

.section  .bss                # Section declaration

.lcomm    cwdstr, PATH_MAX    # Space for working dir

.text                         # Section declaration
  .global _start              # Export entry point for linker

_start:

# Get current working directory ...

  movl  $cwdstr, %ebx         # 1st arg : buffer
  movl  $PATH_MAX, %ecx       # 2nd arg : max len
  movl  $__NR_getcwd, %eax    # System call number
  int   $KERNEL               # Call kernel

# Put in a newline ...

  movl  $cwdstr, %ebx         # Get address into ebx
  addl  %eax, %ebx            # Add string length
  movb  $NEWLINE, -1 (%ebx)   # Move in a newline

# Print to stdout ...

  movl  $STDOUT, %ebx         # 1st arg : fd
  movl  $cwdstr, %ecx         # 2nd arg : pointer to message
  movl  %eax, %edx            # 3rd arg : message length
  movl  $__NR_write, %eax     # System call number
  int   $KERNEL               # Call kernel

# Exit ...

  movl  $OK_EXIT, %ebx        # 1st arg : exit code
  movl  $__NR_exit, %eax      # System call number
  int   $KERNEL               # Call kernel