read_line Subroutine

   subroutine read_line(self, unit, form, iostat, iomsg)
   !< Read line (record) from a connected unit.
   !<
   !< The line is read as an ascii stream read until the eor is reached.
   !<
   !< @note For unformatted read only `access='stream'` is supported with new_line as line terminator.
   !<
   !<```fortran
   !< type(string)      :: astring
   !< type(string)      :: line(3)
   !< integer           :: iostat
   !< character(len=99) :: iomsg
   !< integer           :: scratch
   !< integer           :: l
   !< logical           :: test_passed(6)
   !< line(1) = ' Hello World!   '
   !< line(2) = 'How are you?  '
   !< line(3) = '   All say: "Fine thanks"'
   !< open(newunit=scratch, status='SCRATCH')
   !< write(scratch, "(A)") line(1)%chars()
   !< write(scratch, "(A)") line(2)%chars()
   !< write(scratch, "(A)") line(3)%chars()
   !< rewind(scratch)
   !< l = 0
   !< iostat = 0
   !< do
   !<   l = l + 1
   !<   call astring%read_line(unit=scratch, iostat=iostat, iomsg=iomsg)
   !<   if (iostat/=0.and..not.is_iostat_eor(iostat)) then
   !<     exit
   !<   else
   !<     test_passed(l) = (astring==line(l))
   !<   endif
   !< enddo
   !< close(scratch)
   !< open(newunit=scratch, status='SCRATCH', form='UNFORMATTED', access='STREAM')
   !< write(scratch) line(1)%chars()//new_line('a')
   !< write(scratch) line(2)%chars()//new_line('a')
   !< write(scratch) line(3)%chars()//new_line('a')
   !< rewind(scratch)
   !< l = 0
   !< iostat = 0
   !< do
   !<   l = l + 1
   !<   call astring%read_line(unit=scratch, iostat=iostat, iomsg=iomsg, form='UnfORMatteD')
   !<   if (iostat/=0.and..not.is_iostat_eor(iostat)) then
   !<     exit
   !<   else
   !<     test_passed(l+3) = (astring==line(l))
   !<   endif
   !< enddo
   !< close(scratch)
   !< print '(L1)', all(test_passed)
   !<```
   !=> T <<<
   class(string),    intent(inout)           :: self    !< The string.
   integer,          intent(in)              :: unit    !< Logical unit.
   character(len=*), intent(in),    optional :: form    !< Format of unit.
   integer,          intent(out),   optional :: iostat  !< IO status code.
   character(len=*), intent(inout), optional :: iomsg   !< IO status message.
   type(string)                              :: form_   !< Format of unit, local variable.
   integer                                   :: iostat_ !< IO status code, local variable.
   character(len=:),          allocatable    :: iomsg_  !< IO status message, local variable.
   character(kind=CK, len=:), allocatable    :: line    !< Line storage.
   character(kind=CK, len=1)                 :: ch      !< Character storage.

   form_ = 'FORMATTED' ; if (present(form)) form_ = form ; form_ = form_%upper()
   iomsg_ = repeat(' ', 99) ; if (present(iomsg)) iomsg_ = iomsg
   line = ''
   select case(form_%chars())
   case('FORMATTED')
      do
         read(unit, "(A)", advance='no', iostat=iostat_, iomsg=iomsg_, err=10, end=10, eor=10) ch
         line = line//ch
      enddo
   case('UNFORMATTED')
      do
         read(unit, iostat=iostat_, iomsg=iomsg_, err=10, end=10) ch
         if (ch==new_line('a')) then
            iostat_ = iostat_eor
            exit
         endif
         line = line//ch
      enddo
   endselect
   10 if (line/='') self%raw = line
   if (present(iostat)) iostat = iostat_
   if (present(iomsg)) iomsg = iomsg_
   endsubroutine read_line