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Expected output for 'h5diff -p -4 h5diff_basic1.h5 h5diff_basic2.h5 g1/dset3 g1/dset4'
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<-p -4> is not a valid option
usage: h5diff [OPTIONS] file1 file2 [obj1[obj2]] 
  file1                    File name of the first HDF5 file
  file2                    File name of the second HDF5 file
  [obj1]                   Name of an HDF5 object, in absolute path
  [obj2]                   Name of an HDF5 object, in absolute path
  OPTIONS
   -h, --help              Print a usage message and exit
   -V, --version           Print version number and exit
   -r, --report            Report mode. Print differences
   -v, --verbose           Verbose mode. Print differences, list of objects
   -q, --quiet             Quiet mode. Do not do output
   -n C, --count=C         Print differences up to C number
   -d D, --delta=D         Print difference when greater than limit D
   -p R, --relative=R      Print difference when greater than relative limit R

  C - is a positive integer
  D - is a positive number. Compare criteria is |a - b| > D
  R - is a positive number. Compare criteria is |(b-a)/a| > R

h5diff has four modes of output:
 Normal mode: print the number of differences found and where they occured
 Report mode: print the above plus the differences
 Verbose mode: print the above plus a list of objects and warnings
 Quiet mode: do not print output (h5diff always returns an exit code of 1 when differences are found)

Examples of use:

1) h5diff file1 file2 /g1/dset1 /g1/dset2

   Compares object '/g1/dset1' in file1 with '/g1/dset2' in file2

2) h5diff file1 file2 /g1/dset1

   Compares object '/g1/dset1' in both files

3) h5diff file1 file2

   Compares all objects in both files

Note)  file1 and file2 can be the same file. Use

   h5diff file1 file1 /g1/dset1 /g1/dset2

   to compare '/g1/dset1' and '/g1/dset2' in the same file

If no objects are specified, h5diff only compares objects with the same absolute path in both files. The compare criteria is: 1) datasets: numerical array differences 2) groups: name string difference 3) datatypes: the return value of H5Tequal 2) links: name string difference of the linked value