C ================================================ C
C //////////////////////////////////////////////// C
C ================================================ C

      program netCDF_rw

      implicit none
      include 'netcdf.inc'

C |---------------------------------------------------------|
C | This programme demonstrates several uses of the NetCDF- |
C | libraries via the NetCDF-FORTRAN interface:             |
C |                                                         |
C | Making an inquire call (get info), reading an .nc file, |
C | defining dimensions and variables, assigning attribites |
C | to variables, creating and writing in an .nc file       |
C |                                                         |
C | It gets data from an .nc file and writes it into a      |
C | newly defined .nc file.                                 |
C |                                                         |
C | --------------------------------------------------------|
C | NOTE: Make sure the netcdf libraries are installed and  |
C | the paths to bin,lib and include files are set          |
C | correctly (for example in .bashrc,.cshrc or in the      |
C | compile command using -I/inc/path and -L/lib/path) and  |
C | libraries are included with -lnetcdff                   |
C |                                                         |
C | --------------------------------------------------------|
C | This programme was tested with the netcdf-4.1.3 package |
C | configured with '--disable-netcdf-4 --disable-dap' and  | 
C | compiled with gfortran. As an example dataset, the NOAA | 
C | monthly mean SST's were used.                           |
C | (Available on www.esrl.noaa.gov)                        |              
C |                                                         |
C | General information on netcdf: www.unidata.ucar.edu     |
C | Specific questions about this script:                   |
C | sebastian.mutz@uni-tuebingen.de                         |
C |---------------------------------------------------------|

C ------------------------------------------------ C
C ---- VARIABLES and PARAMETERS ------------------ C
C ------------------------------------------------ C

      character path*34,infile*40,outfile*40
      integer x,y,t

      ! file specifics
      integer nx,ny,nt,ndim
      parameter(nx=360,ny=180,nt=361,ndim=3)

      ! dataset variables
      real xvar(nx),yvar(ny),tvar(nt)        ! dimension variables
      real cvar(nx,ny,nt)                    ! data

      ! variable names and attributes (optional but recommended)
      character*(*)x_dname,y_dname,t_dname           ! dimension names
      parameter(x_dname='lon',y_dname='lat',t_dname='time')
      character*(*)x_name,y_name,t_name,cvar_name    ! variable names
      parameter(x_name='longitude',y_name='latitude',t_name='time',
     $     cvar_name='sst')
      character*(*)att                               ! attribute name
      parameter(att='units')
      character*(*)x_att,y_att,t_att,cvar_att        ! variable attributes
      parameter(x_att='degrees east',y_att='degrees north',
     $     t_att='days since 1800-1-1 00:00:00',cvar_att='degC')

      ! netcdf 'communication' variables
      integer cvar_id,x_id,y_id,t_id         ! variable IDs
      integer x_did,y_did,t_did,dimid(ndim)  ! dimension IDs
      integer state,ncid                     ! return value and file ID
      integer nrecs,recid,dim,var,gatt,unlim ! for inquire call
      character*(nf_max_name) recname

      path='/home/sebastian/research/TIP/data/'  ! path to dataset
      infile='editable_sst.mnmean.nc'            ! dataset name

C ------------------------------------------------- C
C ==== INSTRUCTIONS =============================== C
C ------------------------------------------------- C

C ==== Inquire call =============================== C

      print*
      print*, 'Info on ', infile
      print*, '===================================='

      ! opening file
      state = nf_open(path//infile,nf_nowrite,ncid)           
      if (state .ne. nf_noerr) call handle_err(state)

      ! inquire call
      state = nf_inq(ncid,dim,var,gatt,unlim)           
      if (state .ne. nf_noerr) call handle_err(state)

      ! counting dimension variables and values for each
      do x=1,dim          
        state = nf_inq_dim(ncid,x,recname,nrecs)           
        if (state .ne. nf_noerr) call handle_err(state)
        print '(a13,i2,a4,a6,a8,i4)', 
     1         '   Dimension ',x,'         :   ',recname,'Count: ',nrecs
      enddo
   
      print*, '   > netCDF file checked'
      print*

C ==== Read existing netCDF file ================== C

      print*, 'Reading file ', infile
      print*, '===================================='

      state = nf_inq_varid(ncid,'lon',x_id)
	      state=nf_get_var_real(ncid,x_id,xvar)
	      if (state .ne. nf_noerr) call handle_err(state)
              print*, '  (1) Longitudes read'

      state = nf_inq_varid(ncid,'lat',y_id)
	      state=nf_get_var_real(ncid,y_id,yvar)
	      if (state .ne. nf_noerr) call handle_err(state)
              print*, '  (2) Latitudes read'
      
      state = nf_inq_varid(ncid,'time',t_id)
	      state=nf_get_var_real(ncid,t_id,tvar)
	      if (state .ne. nf_noerr) call handle_err(state)
              print*, '  (3) Times read'

      state = nf_inq_varid(ncid,'sst',cvar_id)
              state=nf_get_var_real(ncid,cvar_id,cvar)
              if (state.ne.nf_noerr) call handle_err(state)
              print*, '  (4) Data variable read'
    
      print*, '   > Read complete'
      print*

C ==== Creating and writing in new file =========== C

      outfile='mod.'//infile
 
      print*, 'Writing in ', outfile
      print*, '===================================='

      ! create file
      state = nf_create(path//outfile,nf_clobber,ncid)
	      if (state .ne. nf_noerr) call handle_err(state)

      ! define dimensions
              print*, '  > Define dimensions'
      state = nf_def_dim(ncid,x_dname,nx,x_did)
	      if (state .ne. nf_noerr) call handle_err(state)
              print*, '    (1) Longitude dimension defined'
      state = nf_def_dim(ncid,y_dname,ny,y_did)
	      if (state .ne. nf_noerr) call handle_err(state)
              print*, '    (2) Latitude dimension defined'
      state = nf_def_dim(ncid,t_dname,nt,t_did)
	      if (state .ne. nf_noerr) call handle_err(state)
              print*, '    (3) Time dimension defined'
              print*

      ! define variables
              print*, '  > Define variables'
      state = nf_def_var(ncid,x_name,nf_real,1,x_did,x_id)
	      if (state .ne. nf_noerr) call handle_err(state)
              print*, '    (1) Longitude variable defined'
      state = nf_def_var(ncid,y_name,nf_real,1,y_did,y_id)
	      if (state .ne. nf_noerr) call handle_err(state)
              print*, '    (2) Latitude variable defined'
      state = nf_def_var(ncid,t_name,nf_real,1,t_did,t_id)
	      if (state .ne. nf_noerr) call handle_err(state)
              print*, '    (3) Time variable defined'

      ! dimension IDs for data variable
      dimid(1)=x_did
      dimid(2)=y_did
      dimid(3)=t_did

      ! define data as type real, with ndim dimensions (with ndim dimension IDs)
      state = nf_def_var(ncid,cvar_name,nf_real,ndim,dimid,cvar_id)
	      if (state .ne. nf_noerr) call handle_err(state)
              print*, '    (4) Data variable defined'
              print*

      ! assign attributes to variables
      print*, '  > Assign attributes to variables'
      state = nf_put_att_text(ncid,x_id,att,len(x_att),x_att)
	      if (state .ne. nf_noerr) call handle_err(state)
              print*, '    (1) Longitude attribute added'
      state = nf_put_att_text(ncid,y_id,att,len(y_att),y_att)
	      if (state .ne. nf_noerr) call handle_err(state)
              print*, '    (2) Latitude attribute added'
      state = nf_put_att_text(ncid,t_id,att,len(t_att),t_att)
	      if (state .ne. nf_noerr) call handle_err(state)
              print*, '    (3) Time attribute added'
      state = nf_put_att_text(ncid,cvar_id,att,len(cvar_att),cvar_att)
	      if (state .ne. nf_noerr) call handle_err(state)
              print*, '    (4) Data attribute added'
              print*
              ! note:len specifies string length, can also type in manually

      ! end define mode
      state = nf_enddef(ncid)
              if (state .ne. nf_noerr) call handle_err(state)

      ! put variables in file
      print*, '  > Write variables in file'
      state = nf_put_var_real(ncid,x_id,xvar)
              if (state .ne. nf_noerr) call handle_err(state)
              print*, '    (1) Longitude added to file'
      state = nf_put_var_real(ncid,y_id,yvar)
              if (state .ne. nf_noerr) call handle_err(state)
              print*, '    (2) Latitude added to file'
      state = nf_put_var_real(ncid,t_id,tvar)
              if (state .ne. nf_noerr) call handle_err(state)
              print*, '    (3) Time added to file'
      state = nf_put_var_real(ncid,cvar_id,cvar)
              if (state .ne. nf_noerr) call handle_err(state)
              print*, '    (4) Data variable added to file'
              print*

      ! close file
      state = nf_close(ncid)
              if (state.ne.nf_noerr) call handle_err(state)
              print*, '  > File closed: ', path//outfile           

      end

C ================================================== C
C ////////////////////////////////////////////////// C
C ================================================== C

      subroutine handle_err(errcode)
      implicit none
      include 'netcdf.inc'
      integer errcode
      print *, 'Error: ', nf_strerror(errcode)
      stop
      end