anchor.diff:         atom1_id = 1
          atom2_tag = "O"
          latv = 10.0014453
  -       file_in = "m.trj"
  +       file_in = "test.xyz"
          file_out = "test.out"
          file_lattice = "lat.dat"
   c      ---------------------------      
  
positive.code:        subroutine mask_all(n,c,atag,oc,mid,mtag)
         implicit none
         integer n
         double precision c(n,3)
         character*(*) atag(n)
         logical oc(n)
         integer mid
  
negative.code:           end if
          end do
          message = "reading "//bigbuf
          read(bigbuf,*,err=911) atag(i),(c(k,i),k=1,3)
          n0=i
         end do
  c      check if all atoms were read
  