Re: sum: does not always display filename

[Jim Meyering]

"Matt Weinstein" <address@hidden> wrote:
> sum does not output the filename of the file being sum(med) if only one
> filename is supplied.
...
> This is inconsistent and undocumented to the best of my knowledge.

That behavior *is* documented.
Here's the relevant part of `info sum':

     `sum' prints the checksum for each FILE followed by the number of
  blocks in the file (rounded up).  If more than one FILE is given, file
  names are also printed (by default).  (With the `--sysv' option,
  corresponding file names are printed when there is at least one file
  argument.)