write_restart_file Subroutine

   subroutine write_restart_file(mesh, flow, params, fields, species, energy, transport, step, time, chemistry_accum_dt)
      type(mesh_t), intent(in) :: mesh
      type(flow_mpi_t), intent(inout) :: flow
      type(case_params_t), intent(in) :: params
      type(flow_fields_t), intent(in) :: fields
      type(species_fields_t), intent(in) :: species
      type(energy_fields_t), intent(in) :: energy
      type(transport_properties_t), intent(in) :: transport
      integer, intent(in) :: step
      real(rk), intent(in) :: time
      real(rk), intent(in), optional :: chemistry_accum_dt

      character(len=path_len) :: restart_dir, filename
      character(len=16) :: step_text
      integer :: ierr

      if (.not. params%write_restart) return
      if (params%restart_interval <= 0) return
      if (mod(step, params%restart_interval) /= 0 .and. step /= params%nsteps) return

      call restart_directory(params, restart_dir)
      if (flow%rank == 0) then
         call execute_command_line('mkdir -p ' // trim(restart_dir))
      end if
      call MPI_Barrier(flow%comm, ierr)
      if (ierr /= MPI_SUCCESS) call fatal_error('restart', 'MPI_Barrier failed before restart write')

      write(step_text, '(i8.8)') step
      filename = trim(restart_dir) // '/restart_' // trim(step_text) // '.rst'
      if (present(chemistry_accum_dt)) then
         call write_restart_to_path(trim(filename), mesh, flow, params, fields, species, energy, transport, step, time, chemistry_accum_dt)
      else
         call write_restart_to_path(trim(filename), mesh, flow, params, fields, species, energy, transport, step, time, zero)
      end if

      if (flow%rank == 0) then
         if (trim(params%terminal_detail) == 'full') then
            write(output_unit,'(a,a)') 'wrote restart: ', trim(filename)
         end if
         call prune_restart_files(params, trim(restart_dir))
      end if
   end subroutine write_restart_file