format elf executable

entry main

;syscalls
SYSCALL_EXIT           equ 1
SYSCALL_READ           equ 3
SYSCALL_WRITE          equ 4
SYSCALL_SELECT         equ 82

;standard I/O
STDIN    equ 0
STDOUT equ 1

;useful special characters
LF   equ 0x0a

;various defines
__NFDBITS   equ 8 * 4
__NFD_SETSIZE      equ 1024

;structs
struc timeval secs, usec{
  .tv_secs dd secs ;seconds
   .tv_usec dd usec ;microseconds
}

;static data
segment readable writeable

fds rd __NFD_SETSIZE / __NFDBITS
t timeval 5,0

;--------
segment executable
main:
     ;clear fds
  mov eax, 0
  mov ecx, __NFD_SETSIZE / __NFDBITS
  mov edi, fds
        rep stos dword [edi]

    ;select
     bts [fds], STDIN
    mov eax, SYSCALL_SELECT
     mov ebx, STDIN + 1 ;nfds
    mov ecx, fds ;readfds
       xor edx, edx ;writefds
      xor esi, esi ;exceptfds
     mov edi, t ;timeout
 int 0x80

        test eax, eax ;eax -> -errno
     js exit

 ;exit normally
      mov eax, 0

exit:
 ;exit with error-code
       mov ebx, eax
        neg ebx
     mov eax, SYSCALL_EXIT
       int 0x80    

SYSCALL_SELECT          equ 82    

SYSCALL_SELECT          equ 142