gistfile1.asm

; Write contents from stdin to a given file
section .rodata
errnofile:      db "No filename given", 10
errnofilelen:   equ $ - errnofile
errnocreate:    db "Couldn't create file", 10
errnocreatelen: equ $ - errnocreate
errnowrite:    db "Couldn't write file", 10
errnowritelen: equ $ - errnowrite

section .bss
input: resb 1024
inputlen: equ $ - input

section .text
global _start

; simple exit, ebx contains exit code.
exit:
  mov eax, 1
  int 80h

; no file name given, print error exit with 1.
nofile:
  mov eax, 4
  mov ebx, 2
  mov ecx, errnofile
  mov edx, errnofilelen
  int 80h

  mov ebx, 1
  jmp exit

; couldn't create, print error exit with 1.
nocreate:
  mov eax, 4
  mov ebx, 2
  mov ecx, errnocreate
  mov edx, errnocreatelen
  int 80h

  mov ebx, 1
  jmp exit

; couldn't write, print error exit with 1.
nowrite:
  mov eax, 4
  mov ebx, 2
  mov ecx, errnowrite
  mov edx, errnowritelen
  int 80h

  mov ebx, 1
  jmp exit

_start:
  pop ebx
  cmp ebx, 1
  je nofile
  pop ebx
  pop ebx

  ; create file
  mov eax, 8
  mov ecx, 0q600
  int 80h
  test eax, eax
  js nocreate
  push eax

  ; read stdin
  mov eax, 3
  mov ebx, 0
  mov ecx, input
  mov edx, inputlen
  int 80h

  ; write stdin to file
  mov eax, 4
  pop ebx
  mov ecx, input
  mov edx, inputlen
  int 80h
  test eax, eax
  js nowrite

  ; close file
  mov eax, 6
  int 80h
  mov ebx, 0
  jmp exit