cis-lclient05:~/2012/system>more greeting.s
.section .data

   prompt_str:
      .ascii "Enter Your Name: "
   pstr_end:
      .set STR_SIZE, pstr_end - prompt_str
   greet_str:
      .ascii "Hello "
   gstr_end:
      .set GSTR_SIZE, gstr_end - greet_str

.section .bss

// Reserve 32 bytes of memory
   .lcomm  buff, 32

// A macro with two parameters
//  implements the write system call
   .macro write str, str_size 
      movl  $4, %eax
      movl  $1, %ebx
      movl  \str, %ecx
      movl  \str_size, %edx
      int   $0x80
   .endm
// Implements the read system call
   .macro read buff, buff_size
      movl  $3, %eax
      movl  $0, %ebx
      movl  \buff, %ecx
      movl  \buff_size, %edx
      int   $0x80
   .endm

.section .text
   .globl _start

   _start:
      write $prompt_str, $STR_SIZE
      read  $buff, $32
// Read returns the length in eax
      pushl %eax

// Print the hello text
      write $greet_str, $GSTR_SIZE
      popl  %edx
// edx = length returned by read
      write $buff, %edx

   _exit:
      movl  $1, %eax
      movl  $0, %ebx
      int   $0x80

cis-lclient05:~/2012/system>as -o greeting.o greeting.s
cis-lclient05:~/2012/system>ln -o greeting greeting.o
ln: invalid option -- 'o'
Try `ln --help' for more information.
cis-lclient05:~/2012/system>ld -o greeting greeting.o
cis-lclient05:~/2012/system>greeting
Enter Your Name: Dr. Bob
Hello Dr. Bob
cis-lclient05:~/2012/system>echo $?
0
cis-lclient05:~/2012/system>