| Re: Is_netCDF Function [message #38737] |
Fri, 26 March 2004 07:42 |
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Paul Van Delst[1]
Messages: 1157
Registered: April 2002
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Senior Member |
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Kenneth P. Bowman wrote:
> In article <MPG.1acd1c3c46279728989715@news.frii.com>,
> David Fanning <david@dfanning.com> wrote:
>
>
>> Isn't there a function to tell if a file is a netCDF file or not?
>> I've looked everywhere but the right place. :-(
>
>
> There's the function NCDF_EXITS, which sounds like it ought to do what
> you want, but it doesn't.
>
> To tell if a file is a netCDF file, try opening it and be prepared to
> handle the error.
>
> IDL> id = ncdf_open('.tcshrc')
> % NCDF_OPEN: Unable to open the file ".tcshrc". (NC_ERROR=-51)
> % Execution halted at: $MAIN$
That's what I do. I wrapped the above in an is_ncdf() function. The error value, -51,
indicates that the file is not an netCDF format file. Here's the complete list, with a
short description, from the netcdf.h file supplied with the netcdf library:
/*
* The netcdf version 3 functions all return integer error status.
* These are the possible values, in addition to certain
* values from the system errno.h.
*/
#define NC_ISSYSERR(err) ((err) > 0)
#define NC_NOERR 0 /* No Error */
#define NC_EBADID (-33) /* Not a netcdf id */
#define NC_ENFILE (-34) /* Too many netcdfs open */
#define NC_EEXIST (-35) /* netcdf file exists && NC_NOCLOBBER */
#define NC_EINVAL (-36) /* Invalid Argument */
#define NC_EPERM (-37) /* Write to read only */
#define NC_ENOTINDEFINE (-38) /* Operation not allowed in data mode */
#define NC_EINDEFINE (-39) /* Operation not allowed in define mode */
#define NC_EINVALCOORDS (-40) /* Index exceeds dimension bound */
#define NC_EMAXDIMS (-41) /* NC_MAX_DIMS exceeded */
#define NC_ENAMEINUSE (-42) /* String match to name in use */
#define NC_ENOTATT (-43) /* Attribute not found */
#define NC_EMAXATTS (-44) /* NC_MAX_ATTRS exceeded */
#define NC_EBADTYPE (-45) /* Not a netcdf data type */
#define NC_EBADDIM (-46) /* Invalid dimension id or name */
#define NC_EUNLIMPOS (-47) /* NC_UNLIMITED in the wrong index */
#define NC_EMAXVARS (-48) /* NC_MAX_VARS exceeded */
#define NC_ENOTVAR (-49) /* Variable not found */
#define NC_EGLOBAL (-50) /* Action prohibited on NC_GLOBAL varid */
#define NC_ENOTNC (-51) /* Not a netcdf file */
#define NC_ESTS (-52) /* In Fortran, string too short */
#define NC_EMAXNAME (-53) /* NC_MAX_NAME exceeded */
#define NC_EUNLIMIT (-54) /* NC_UNLIMITED size already in use */
#define NC_ENORECVARS (-55) /* nc_rec op when there are no record vars */
#define NC_ECHAR (-56) /* Attempt to convert between text & numbers */
#define NC_EEDGE (-57) /* Edge+start exceeds dimension bound */
#define NC_ESTRIDE (-58) /* Illegal stride */
#define NC_EBADNAME (-59) /* Attribute or variable name
contains illegal characters */
/* N.B. following must match value in ncx.h */
#define NC_ERANGE (-60) /* Math result not representable */
#define NC_ENOMEM (-61) /* Memory allocation (malloc) failure */
Of course, one should really define these in a netcdf.pro include file since I'm sure the
actual value associated with NC_ENOTNC, -51, could possibly chane in future releases (of
netcdf or IDL... or both!)
paulv
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| Re: Is_netCDF Function [message #38738 is a reply to message #38737] |
Fri, 26 March 2004 06:56  |
mmiller3
Messages: 81
Registered: January 2002
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Member |
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>>>> > "Kenneth" == Kenneth P Bowman <kpb@null.com> writes:
> To tell if a file is a netCDF file, try opening it and be
> prepared to handle the error.
We check for netcdf files like this:
header = bytarr(3)
openr, lun, filename, /get_lun
readu, lun, header
free_lun, lun
if string(header) eq 'CDF' then print, 'I think this might be a netcdf file...'
This is based on the file format specs from Unidata
( http://www.unidata.ucar.edu/packages/netcdf/guidec/guidec-18 .html)
Mike
--
Michael A. Miller mmiller3@iupui.edu
Imaging Sciences, Department of Radiology, IU School of Medicine
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| Re: Is_netCDF Function [message #38751 is a reply to message #38738] |
Thu, 25 March 2004 17:09 |
Kenneth P. Bowman
Messages: 585
Registered: May 2000
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Senior Member |
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In article <MPG.1acd1c3c46279728989715@news.frii.com>,
David Fanning <david@dfanning.com> wrote:
> Isn't there a function to tell if a file is a netCDF file or not?
> I've looked everywhere but the right place. :-(
There's the function NCDF_EXITS, which sounds like it ought to do what
you want, but it doesn't.
To tell if a file is a netCDF file, try opening it and be prepared to
handle the error.
IDL> id = ncdf_open('.tcshrc')
% NCDF_OPEN: Unable to open the file ".tcshrc". (NC_ERROR=-51)
% Execution halted at: $MAIN$
Ken
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