GNU bug report logs - #54614
GNU Sed 's/.../\n/' disagreement with POSIX

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

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: bug-sed <at> gnu.org
Subject: GNU Sed 's/.../\n/' disagreement with POSIX
Date: Mon, 28 Mar 2022 10:20:41 -0700

POSIX says that this shell command:

 echo 'abc' | sed 's/b/\n/g'

should output 'anc', but with GNU Sed it outputs two lines 'a' and 'c', 
even if POSIXLY_CORRECT is set.

Traditional Sed (e.g., Solaris, AIX 7) conforms to POSIX. FreeBSD Sed 
agrees with GNU Sed though, and I would guess that that GNU Sed's 
behavior is probably more expected. However, this disagreement with 
POSIX should be documented in the GNU Sed manual (and the manual should 
recommend backslash-newline over backslash-'n' for portability), and if 
POSIXLY_CORRECT is set, GNU Sed should conform to POSIX.

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

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: bug-sed <at> gnu.org
Subject: Re: GNU Sed 's/.../\n/' disagreement with POSIX
Date: Mon, 28 Mar 2022 11:39:38 -0700

On 3/28/22 10:20, Paul Eggert wrote:
> POSIX says that this shell command:
> 
>   echo 'abc' | sed 's/b/\n/g'
> 
> should output 'anc', but with GNU Sed it outputs two lines 'a' and 'c', 
> even if POSIXLY_CORRECT is set.

Oh, a further reading of the POSIX spec indicates that the behavior is 
unspecified here. So, please ignore what I wrote about POSIXLY_CORRECT 
etc.; the current GNU Sed behavior is fine. Though it may be helpful to 
document the unportability of \n here.

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