Re: [PATCH] cksum: add --raw option to output a binary digest

[Jim Meyering]

On Sat, Feb 4, 2023 at 10:01 AM Pádraig Brady <P@draigbrady.com> wrote:
>
> On 04/02/2023 16:58, Jim Meyering wrote:
> > On Sat, Feb 4, 2023 at 5:52 AM Pádraig Brady <P@draigbrady.com> wrote:
> >>
> >> --raw output is the most composable format, and also is a
> >> robust way to discard the file name without parsing (escaped) output.
> >
> > Very nice. I applied it and ran all tests, and distcheck. All passed.
> > TIny suggestions:
> >
> >> diff --git a/doc/coreutils.texi b/doc/coreutils.texi
> >> index 4d7d9439d..536301d63 100644
> >> --- a/doc/coreutils.texi
> >> +++ b/doc/coreutils.texi
> >> @@ -4059,6 +4059,14 @@ input digest string as what is output.  I.e., 
> >> removing or adding any
> >>   @opindex --debug
> >>   Output extra information to stderr, like the checksum implementation 
> >> being used.
> >>
> >> +@item --raw
> >> +@opindex --raw
> >> +@cindex raw binary checksum
> >> +Print an unencoded raw binary digest, not hexadecimal.
> >> +No file name or other information is output in this mode.
> >> +Bytes are output in network byte order (big endian).
> >> +This option is ignored with @option{--check}.
> >
> > Maybe insert "only" and use active voice, and do mention the "only one
> > input" limit:
> >
> >    Print only the unencoded raw binary digest for a single file.
> >    Do not output the file name or anything else.
> >    Use network byte order (big endian) where applicable: for bsd, crc and 
> > sysv.
> >    This option is ignored with @option{--check} and works only with a
> > single input.
>
> Much better, thanks.
>
> > Is it worth saying explicitly that unlike other output formats, cksum
> > provides no way to check a --raw checksum?
>
> Yes. I'll change your last line to:
>
>    This option works only with a single input.
>    Unlike other output formats, cksum provides no way to --check a --raw 
> checksum.

I noticed a sporadic test failure when the bsd checksum happened to
have one or more leading zeros.
Compare these:

  $ src/cksum --raw --algorithm=bsd <<< 2|od --endian=big -An -w1024
-tu2|tr -d ' '
  35
  $ src/cksum --untagged --algorithm=bsd <<< 2
  00035     1

At first I thought I'd strip the excess zeros before comparing,
but thought it slightly better to zero-pad any too-narrow value.

The attached seems to do the job:

cksum-raw-zero-padding.diff
Description: Binary data