GNU bug report logs - #28140
Here is a possible bug in documentation for 4.4

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

From: bamber ward <dlward134 <at> gmail.com>
To: bug-sed <at> gnu.org
Subject: Here is a possible bug in documentation for 4.4
Date: Fri, 18 Aug 2017 16:34:13 +0100

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

manual 4.4
section 7-8
 sed -E ':x {N ; s/\n/ /g ; s/(.{40,40})/\1\n/ ; /\n/!bx ; P ;D}'
does not work as described. Change line length , say to 5
  sed -E ':x {N ; s/\n/ /g ; s/(.{5,5})/\1\n/ ; /\n/!bx ; P ;D}'
cat line_wrap_input :
apple grape
pear peach
pomengranate

~/sed/code-> sed -E ':x {N ; s/\n/ /g ; s/(.{5,5})/\1\n/ ; /\n/!bx ; P ;
D}' \  line_wrap_input
apple
 grap
e pear peach pomengranate


~/sed/code->

This seems to work:

#!/bin/sed -rf
# line_wrap.sed (

:x
{
   N
   s/\n/ /g
   :y
   s_(.{40,40})_\1\n_
    /.{40,40}/  P
   s/.*\n//
   ty
   /\n/!bx

}

Best Wishes
David L Ward

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

Message #8 received at 28140 <at> debbugs.gnu.org (full text, mbox):

From: Assaf Gordon <assafgordon <at> gmail.com>
To: bamber ward <dlward134 <at> gmail.com>, 28140 <at> debbugs.gnu.org
Subject: Re: bug#28140: Here is a possible bug in documentation for 4.4
Date: Fri, 25 Aug 2017 09:42:32 -0600

Hello,

On 18/08/17 09:34 AM, bamber ward wrote:
> manual 4.4
> section 7-8
>  sed -E ':x {N ; s/\n/ /g ; s/(.{40,40})/\1\n/ ; /\n/!bx ; P ;D}'
> does not work as described.

Thank you for reporting this.

Indeed, the sed program does not wrap the last line ('D' does not
provide a way to loop over the last line in case it's longer than 40
characters).

> #!/bin/sed -rf
> # line_wrap.sed (
> 
> :x
> {
>    N
>    s/\n/ /g
>    :y
>    s_(.{40,40})_\1\n_
>     /.{40,40}/  P
>    s/.*\n//
>    ty
>    /\n/!bx
> 
> }

I wonder if the following program would suffice
(very similar to yours, but without conditional P, just to simplify the
example code in the manual).

sed -E ':x
        {
          N
          s/\n/ /g
          :y
          s/(.{20,20})/\1\n/
          /\n/!bx
          P
          s/.*\n//
          ty
        }'


regards,
 - assaf

Message #11 received at 28140 <at> debbugs.gnu.org (full text, mbox):

From: Assaf Gordon <assafgordon <at> gmail.com>
To: bamber ward <dlward134 <at> gmail.com>, 28140 <at> debbugs.gnu.org
Subject: Re: bug#28140: Here is a possible bug in documentation for 4.4
Date: Thu, 12 Oct 2017 00:31:14 -0600

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

Hello,

> On 18/08/17 09:34 AM, bamber ward wrote:
>> manual 4.4
>> section 7-8
>>  sed -E ':x {N ; s/\n/ /g ; s/(.{40,40})/\1\n/ ; /\n/!bx ; P ;D}'
>> does not work as described.

I'm thinking of the attached patch,
which replaces the overly terse (and incorrect) example
with a longer version with better comments.

Also removed second example to simplify the section.

Comments very welcomed,
 - assaf

[0001-doc-fix-incorrect-line-wrapping-example.patch (text/x-patch, attachment)]

Message #16 received at 28140-done <at> debbugs.gnu.org (full text, mbox):

From: Assaf Gordon <assafgordon <at> gmail.com>
To: bamber ward <dlward134 <at> gmail.com>, 28140-done <at> debbugs.gnu.org
Subject: Re: bug#28140: Here is a possible bug in documentation for 4.4
Date: Sat, 28 Oct 2017 21:28:22 -0600

On 2017-10-12 12:31 AM, Assaf Gordon wrote:
>> On 18/08/17 09:34 AM, bamber ward wrote:
>>> manual 4.4
>>> section 7-8
>>>   sed -E ':x {N ; s/\n/ /g ; s/(.{40,40})/\1\n/ ; /\n/!bx ; P ;D}'
>>> does not work as described.
> 
> I'm thinking of the attached patch,
> which replaces the overly terse (and incorrect) example
> with a longer version with better comments.

Push here:
  https://git.savannah.gnu.org/cgit/sed.git/commit/?id=490b4997

regards,
 - assaf

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