So I am working on an x86 Assembly program for Linux using NASM. This program basically asks the user for their name and their favorite color. After doing this and storing the two strings in variables declared in the .bss section, the program prints "No way name of user, favorite color is my favorite color, too!
The problem I am having is that there are enormous spaces in the output because I do not know how long the string was that the user entered, only the length that I declared the buffer to be.
section .data
greet: db 'Hello!', 0Ah, 'What is your name?', 0Ah ;simple greeting
greetL: equ $-greet ;greet length
colorQ: db 'What is your favorite color?' ;color question
colorL: equ $-colorQ ;colorQ length
suprise1: db 'No way '
suprise1L equ $-suprise1
suprise3: db ' is my favorite color, too!', 0Ah
section .bss
name: resb 20 ;user's name
color: resb 15 ;user's color
section .text
global _start
_start:
greeting:
mov eax, 4
mov ebx, 1
mov ecx, greet
mov edx, greetL
int 80 ;print greet
getname:
mov eax, 3
mov ebx, 0
mov ecx, name
mov edx, 20
int 80 ;get name
askcolor:
;asks the user's favorite color using colorQ
getcolor:
mov eax, 3
mov ebx, 0
mov ecx, name
mov edx, 20
int 80
thesuprise:
mov eax, 4
mov ebx, 1
mov ecx, suprise1
mov edx, suprise1L
int 80
mov eax, 4
mov ebx, 1
mov ecx, name
mov edx, 20
int 80
;write the color
;write the "suprise" 3
mov eax, 1
mov ebx, 0
int 80
The code for what I am doing is above. Does anyone have a good method for finding the length of the entered string, or of taking in a character at a time to find out the length of the string?
BUFSIZ
(typically 512). \$\endgroup\$ – Jeff Mercado Oct 23 '11 at 19:39int 80h
is not the most interesting use of assembly. Things like doing file I/O or maintaining dynamically-resized buffers make a lot more sense in C. What you will have with this approach is an assembly program that calls C functions (either through a software interrupt in the case of syscalls orcall
instruction in the case oflibc
), and that won't really teach you idiomatic x86 assembly. \$\endgroup\$ – asveikau Oct 24 '11 at 1:37realloc
each time the buffer is filled, but this requires more care. \$\endgroup\$ – user786653 Oct 24 '11 at 5:51