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