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

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From: Pádraig Brady <P <at> draigBrady.com>
To: 877i7vyf3l.fsf <at> penguin.cs.ucla.edu, eggert <at> cs.ucla.edu
Cc: 69636 <at> debbugs.gnu.org
Subject: bug#69636: Re: [PATCH] Improve quality of format-checking code for seq.
Date: Fri, 8 Mar 2024 13:47:21 +0000

tag 69636 notabug
close 69636
stop

On 08/03/2024 12:29, User wrote:
> 
> Jim Meyering <jim <at> meyering.net> wrote:
> 
>> Paul Eggert <eggert <at> 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

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