Question $1(4$ points$)$

The following process operates on a file that contains the following lines:

LINE$1$

LINE$2$

LINE$3$

Consider the following code snippet $($the read consumes $6$ characters because of the newline at the end of each line$)$:

int retval;

pid$\_$t childpid $=$ fork$()$;

if $($childpid $>0)\{$

char buf$[1024]$;

fd$1=$ open$("$file$",$ O$\_$RDWR$)$;

retval $=$ read$($fd$1,$ buf, $6)$;

write$($STDOUT$,$ buf, $6)$;

$\}$ else if $($childpid $==0)\{$

char buf$[1024]$;

fd$1=$ open$("$file$",$ O$\_$RDWR$)$;

fd$2=$ dup$($fd$1)$;

retval $=$ read$($fd$1,$ buf, $6)$;

retval $=$ read$($fd$2,$ buf$+6,6)$;

write$($STDOUT$,$ buf, $12)$;

$\}$

Assume the file exists and the fork and the reads and writes succeed.

Which of the following outputs, if any, are possible $($newlines are omitted to make the options easier to read$)?$ Choose all that apply.

LINE$1$ LINE$1$ LINE$2$

LINE$1$ LINE$2$ LINE$1$

LINE$1$ LINE$2$ LINE$3$

LINE$1$ LINE$3$ LINE$2$

LINE$2$ LINE$1$ LINE$3$

None of the above $($explain briefly in comments$)$