NAME

       cdfdiff - compares two classic netCDF files in parallel

SYNOPSIS

       cdfdiff [-b] [-q] [-h] [-v var1,...,varn] [-t diff,ratio] file1 file2

DESCRIPTION

       cdfdiff,  a  sequential  version  of ncmpidiff, compares the contents of the two classic netCDF files and
       reports the first difference found to the standard output. The classic file formats include CDF-1, CDF-2,
       and CDF-5.

       For  variables  and  attributes,  it  reports the array indices of the first element found different when
       option -t is not used. When option -t is used, it reports the element with the  largest  difference  that
       fails to meet the tolerance requirements.

       If neither argument -v nor -h is given besides the two file names, the entire files are compared.

       When  comparing  two  files  entirely,  the  difference between cdfdiff and the Unix command diff is that
       cdfdiff skips the gaps between variables. The gaps may occur when the alignment feature is used to create
       a  new  file. This alignment allows to allocate a larger space for the file header and align the starting
       file offsets of fixed-size variables (see API ncmpi__enddef and PnetCDF hints). Oftentimes, the  contents
       of gaps are non-zero arbitrary bytes. Thus, two netCDF files (of same or different sizes) can be reported
       identical by cdfdiff but not by diff.

OPTIONS

       -b     Verbose mode - print results (same or different) for all components (file, header,  or  variables)
              in comparison

       -q     Quiet  mode  -  print nothing on the command-line output. This also disables verbose mode. When in
              quiet mode, users should check exit status. See below in "EXIT STATUS".

       -h     Compare file header only

       -v var1,...,varn
              Compare only the given list of variables (names separated by comma without space).

       -t diff,ratio
              Compare variables element-wisely with tolerance (diff and ratio separated by comma without space).
              diff is the absolute value of element-wise difference of any two variables.  ratio is the relative
              element-wise ratio, for instance, MAX(x,y) / MIN(x,y) - 1, where x is  an  array  element  from  a
              variable  in  the  first file and y is the corresponding array element of the same variable in the
              second file. Note when this option is used, the comparison will compare the entire  variables  and
              reports  the  element  with  the  largest  difference  that  fails  to  meet  the  both  tolerance
              requirements.

EXIT STATUS

       An exit status of 0 means no differences were found, and 1 means some differences were  found.   Note  on
       VMS-based system, the exit status values are reversed.

SEE ALSO

       ncmpidiff(1), ncmpidump(1), diff(1), pnetcdf(3)

DATE

       PNETCDF_RELEASE_DATE