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Expected output for 'h5diff -p -4 h5diff_test1.h5 h5diff_test2.h5'
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-4 is an invalid option
Usage: h5diff [obj1_name] [obj2_name] [OPTIONS] file1_name [file2_name]
Items in [ ] are optional

[obj1_name]       Name of an HDF5 object
[obj2_name]       Name of an HDF5 object
file1_name        File name of the first HDF5 file
file2_name        File name of the second HDF5 file
[OPTIONS] are:
[-h ]             Print out this information
[-l ]             List contents of file
[-r ]             Print only what objects differ
[-n count]        Print difference up to count number for each variable
[-d delta]        Print difference when it is greater than limit delta
[-p relative]     Print differences which are within a relative error value