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 re‐
       ports  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  op‐
       tion  -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 cdfd‐
       iff 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  require‐
              ments.

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

Printed: 2025-07-18                      PnetCDF PNETCDF_RELEASE_VERSION                              cdfdiff(1)