The parent won't check $\backslash 0($null character$)$ in the data that the child will write to a file so the parent will print "ello from the child"

$$ The parent moves the offset back $20$ bytes so that it can read the message

$$ If the child writes the data, the offset of the file descriptor will increase

$$ Once fork$($ed$,$ the parent and the child will use the same file descriptor number $($copied$)$

$$ The parent won't read any data from the file because the child will close the file descriptor.