/usr/share/zfs/zfs-tests/bin/file_write: invalid option -- '-'
unknown arg -
Usage: /usr/share/zfs/zfs-tests/bin/file_write [-v] -o {create,overwrite,append} -f file_name [-b block_size]
	[-s offset] [-c write_count] [-d data]

Where [data] equal to zero causes chars 0->120 to be repeated throughout, or [data]
equal to 'R' for pseudorandom data.