module link_module
type link
    character(len=1)     :: c
    type (link), pointer :: next => null()
end type link
end module link_module

program ch2201b
use link_module
implicit none
type (link), pointer :: root, current
character(len=:),allocatable:: word
character(len=20):: fname
integer :: io_stat_number = 0
integer::n, i=0

  ! reads an arbitrary amount of text from a file - eof terminates it
  print*,'input file name'
  read '(A)',fname
  open(unit=1,file=fname,status='old')
  
! reads in a character at a time until eof 
  allocate (root)
  read (unit=1,fmt='(a)',advance='no',iostat=io_stat_number) root%c
  if (io_stat_number==-1) then
    nullify (root%next)
  else
    allocate(root%next)
    i = i+1
  end if
  current => root
  do while (associated(current%next))
    current => current%next
    read (unit=1,fmt='(a)',advance='no',iostat=io_stat_number) current%c
    if (io_stat_number==-1) then
      nullify (current%next)
    else
      allocate (current%next)
      i = i+1
    end if
  end do
  print*,i,' characters'
  ! calculate how many characters
  n = i
  allocate(character(len=n)::word)
  i=0
  current => root
  do while (associated(current%next))
    i = i + 1
    word(i:i) = current%c
    current => current%next
  end do
  print*,'text read in is:'
  print*,word
end program ch2201b