bug#69636: Re: [PATCH] Improve quality of format-checking code for seq.

[Pádraig Brady]

tag 69636 notabug
close 69636
stop

On 08/03/2024 12:29, User wrote:
> Jim Meyering <jim@meyering.net> wrote:
>
> > Paul Eggert <eggert@CS.UCLA.EDU> wrote:
> > > * src/seq.c (validate_format): Remove. Migrate its checks into...
> > > (long_double_format): Report an error and exit if an error is found,
> > > instead of returning NULL.  All callers changed.
> > > Use a more-consistent format for diagnostics.
> > > * tests/misc/seq: Adjust to the more-consistent format for diagnostics.
> > > ---
> > >    src/seq.c      |   71
> > +++++++++++++++----------------------------------------
> > >    tests/misc/seq |   10 ++++----
> > >    2 files changed, 25 insertions(+), 56 deletions(-)
> >
> > Thanks.
> > As far as I can see this is a "no semantic change"
> > patch (modulo diagnostics), and it looks fine, so I pushed it.
>
> Dear Paul Eggert and Jim Meyering,
>
>
> Thank you very much for the contribution and care! I hope you have
> awesome and cozy day!
>
> It is a nice addition to check the format in the most and explicitly
> safe cases, I believe, however it disallows to use it in cases when you
> need to just repeat a character without ANY processing directive! For
> example, `a=10; seq -f 'x' -s '' -- "$a";` would print 10 characters "x"
> without the check added prior and significantly (or little but still)
> support development in long codes which would require explicit loops or
> additional dependencies like awesome Perl.
>
> Is it possible to reconsider the check or add an option to ignore the
> format which does not have a required directive? If you know a better
> alternative to the standard utility which would result in the same small
> code but great result, please suggest if possible!
>
> Again, appreciated, and please stay safe!

This suggestion has some merit,
but there are a few ways to generate repetitive data already:

  a=10

  seq $a | xargs printf -- 'x%.0s'

  printf "%${a}s" '' | tr ' ' x

  yes x | head -n$a | tr -d '\n'

Also if only outputting to a terminal, then you can get the
repetition to happen within the terminal code like:

  printf -- "x\e[${a}b"

Therefore I'm not sure it's worth relaxing the validation in seq.

thanks,
Pádraig