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Error reading .nc4 file: 'Unknown file format (NC_ENOTNC)'

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juan ignacio gossn
juan ignacio gossn on 25 Nov 2016
Commented: Rimal Abeed on 7 Jan 2020 at 10:33
Hi there,
Am trying to read a .nc4 file using ncread('filename') and get:
>> ncread('S3A_OL_SRF_20160713_mean_rsr.nc4')
Error using netcdflib
The NetCDF library encountered an error during execution of 'open' function -
'Unknown file format (NC_ENOTNC)'.
Error in netcdf.open (line 60)
[varargout{:}] = netcdflib ( 'open', filename, varargin{1} );
Error in internal.matlab.imagesci.nc/openToRead (line 1249)
this.ncRootid = netcdf.open(this.Filename,'NOWRITE');
Error in internal.matlab.imagesci.nc (line 122)
this.openToRead();
Error in ncread (line 54)
ncObj = internal.matlab.imagesci.nc(ncFile);
Any suggestion will be kindly appreciated
Thanks,
Juancho

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Answers (3)

Tamir Suliman
Tamir Suliman on 25 Nov 2016
It might be corrupted file or over written try to re copy it again that's the message one gets if the file is not there with the netCDF functions.

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juan ignacio gossn
juan ignacio gossn on 27 Nov 2016
Thanks Tamir for your reply, I tried downloading it again and used different versions of matlab but it continues to throw the same message
Juan

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Walter Roberson
Walter Roberson on 25 Nov 2016
Check the first few bytes of the file. If they are 'CDF' then it might be a valid netCDF file but it would not be a NetCDF-4 file. NetCDF-4 files are HDF5 files. If it is NetCDF-4 stored as HDF5, then the file should begin with
Hex: 89 48 44 46 0d 0a 1a 0a
ASCII: \211 HDF \r \n \032 \n

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juan ignacio gossn
juan ignacio gossn on 27 Nov 2016
Thanks Walter for your reply, the first bytes are completely different from what you state:
<!DOCTYPE html><html lang="en" xmlns:fb="http://ogp.me/ns/fb#" xml:lang="en" class="" xmlns="http://www.w3.org/1999/xhtml">
though its termination is clearly .nc4 .... :S
Walter Roberson
Walter Roberson on 27 Nov 2016
It appears that is related to JSON and to Facebook's OpenGraph protocol.
Possibly there is NetCDF-4 represented in the content, but the data structure itself is not NetCDF-4

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juan ignacio gossn
juan ignacio gossn on 21 Dec 2016
Thank you, sorry for my late reply. Actually the file was corrupted, so, nothing to do with Matlab.
Thanks a lot!
Juancho

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