Hi Amanda, > I am using the netCDF-4 data model and a C interface. Is it possible for > you to send me a script where new data is written into an existing file? > I am a bit confused with the way i can read the existing file, its > dimensions, define the new dimensions and write the new data. Yes, but first I'll show you how to create an existing file the easy way, with the "ncgen" utility. Basic use of ncgen is explained in this online workshop section on netCDF utilities: http://www.unidata.ucar.edu/netcdf/workshops/2012/utilities/index.html First, download the CDL text file mslp.cdl from this slide, by clicking on the "mslp.cdl" link and saving the resulting file: http://www.unidata.ucar.edu/netcdf/workshops/2012/utilities/CDL.html Then use ncgen, one of the netCDF utilities stored in the bin/ directory where you installed netCDF, to convert that CDL text file into the corresponding netCDF binary file, mslp.nc, using the command: ncgen -b mslp.cdl Now you can use the attached program, extend.c, to read the mslp.nc file and add some more data to it. You will need to compile extend.c into a program, with something like this: gcc extend.c -o extend -I/usr/local/include -L/usr/local/lib -lnetcdf or you can use the "nc-config" utility to provide the correct include and library flags for the compiler with: gcc extend.c -o extend `nc-config --cflags --libs` If you run the extend program, it will add data for an additional time, which you can verify by looking at the mslp.nc file before running extend and after, using the ncdump utility: ncdump mslp.nc ./extend # You may need to set LD_LIBRARY_PATH to where libnetcdf is installed to run this ncdump mslp.nc You can look at other example netCDF C programs to read and write netCDF data here: http://www.unidata.ucar.edu/netcdf/examples/programs/index.html You can find out more about using utilities like ncgen with netCDF-4 data in this section of the workshop: http://www.unidata.ucar.edu/netcdf/workshops/2012/advanced_utilities/index.html The attached extend.c program doesn't define new dimensions, but you can do that by calling the nc_def_dim function. You can generate a C program that shows this with ncgen: ncgen -l c mslp.cdl > mslp.c --Russ Russ Rew UCAR Unidata Program address@hidden http://www.unidata.ucar.edu Ticket Details =================== Ticket ID: XFU-202199 Department: Support netCDF Priority: Normal Status: Closed
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