GNU bug report logs - #64539
Possible issue with GNU sed documentation regarding the -n option

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Ângelo Otávio Nuffer Nunes <angelonuffer <at> gmail.com>
To: bug-sed <at> gnu.org
Subject: Possible issue with GNU sed documentation regarding the -n option
Date: Sat, 8 Jul 2023 19:35:18 -0300

[Message part 1 (text/plain, inline)]

Dear GNU sed maintainers,

I am writing to report a possible issue with the documentation for the `-n`
option in GNU `sed`. According to the documentation available at
https://www.gnu.org/software/sed/manual/html_node/Command_002dLine-Options.html,
the `-n` option should cause `sed` to only produce output when explicitly
told to via the `p` command.

However, based on responses and comments on this Stack Overflow post (
https://stackoverflow.com/questions/76633771/why-does-gnu-sed-print-output-when-using-the-n-option-with-the-a-command/76639116#76639116)
and my own tests, it appears that several other commands, including `=`,
`l`, `r`, `a`, `i`, and `c`, also produce output even when the `-n` option
is used.

I am still learning how to use GNU `sed`, so I may be misunderstanding
something. However, I wanted to bring this to your attention in case there
is an issue with the documentation that needs to be addressed.

Thank you for your time and for all the work you do on GNU `sed`.

Best regards,
Ângelo Nuffer

[Message part 2 (text/html, inline)]

Message #8 received at 64539 <at> debbugs.gnu.org (full text, mbox):

From: Vincent Lefevre <vincent <at> vinc17.net>
To: Ângelo Otávio Nuffer Nunes <angelonuffer <at> gmail.com>
Cc: 64539 <at> debbugs.gnu.org
Subject: Re: Possible issue with GNU sed documentation regarding the -n option
Date: Wed, 24 Jul 2024 11:19:47 +0200

Hi,

On 2023-07-08 19:35:18 -0300, Ângelo Otávio Nuffer Nunes wrote:
> I am writing to report a possible issue with the documentation for the `-n`
> option in GNU `sed`. According to the documentation available at
> https://www.gnu.org/software/sed/manual/html_node/Command_002dLine-Options.html,
> the `-n` option should cause `sed` to only produce output when explicitly
> told to via the `p` command.
> 
> However, based on responses and comments on this Stack Overflow post (
> https://stackoverflow.com/questions/76633771/why-does-gnu-sed-print-output-when-using-the-n-option-with-the-a-command/76639116#76639116)
> and my own tests, it appears that several other commands, including `=`,
> `l`, `r`, `a`, `i`, and `c`, also produce output even when the `-n` option
> is used.

Perhaps the doc of -n implicitly means that this is specifically the
output of the current pattern space at the end of a cycle (as done by
default, which is what this paragraph is about). Said otherwise, with
the -n option, to get the same behavior as the default one, one would
need a p command at the end of the script.

I think that "via the p command" could be removed, or "for example"
could be added.

-- 
Vincent Lefèvre <vincent <at> vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

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