From unknown Sun Jun 15 08:42:52 2025 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-Mailer: MIME-tools 5.509 (Entity 5.509) Content-Type: text/plain; charset=utf-8 From: bug#70476 <70476@debbugs.gnu.org> To: bug#70476 <70476@debbugs.gnu.org> Subject: Status: `**` GNU extension only works when ERE syntax is enabled Reply-To: bug#70476 <70476@debbugs.gnu.org> Date: Sun, 15 Jun 2025 15:42:52 +0000 retitle 70476 `**` GNU extension only works when ERE syntax is enabled reassign 70476 sed submitter 70476 Dylan Brotherston severity 70476 normal thanks From debbugs-submit-bounces@debbugs.gnu.org Fri Apr 19 19:05:23 2024 Received: (at submit) by debbugs.gnu.org; 19 Apr 2024 23:05:25 +0000 Received: from localhost ([127.0.0.1]:60860 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1rxxI7-0001mZ-Br for submit@debbugs.gnu.org; Fri, 19 Apr 2024 19:05:22 -0400 Received: from lists.gnu.org ([2001:470:142::17]:54944) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1rxsMk-0006Tc-26 for submit@debbugs.gnu.org; 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charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable $ sed --version sed (GNU sed) 4.9 The documentation for sed BRE syntax states: > As a GNU extension, a postfixed regular expression can also be followed b= y *; for example, a** is equivalent to a* https://www.gnu.org/software/sed/manual/sed.html#BRE-syntax But sed reports an error when ** is used in a BRE expression $ seq 10 20 | sed 's/1**//' sed: -e expression #1, char 7: Invalid preceding regular expression and only allows this syntax when ERE syntax is enabled $ seq 10 20 | sed -E 's/1**//' 0 2 3 4 5 6 7 8 9 20 grep, which also implements this GNU extension, allows ** in BRE syntax $ seq 10 20 | grep -o '1**' 1 11 1 1 1 1 1 1 1 1 $ seq 10 20 | grep -oE '1**' 1 11 1 1 1 1 1 1 1 1 Additionally, the documentation for the `--posix` flag states > disable all GNU extensions. ** is specifically documented as a GNU extension, but `--posix` doesn't dis= able the use of ** $ seq 10 20 | sed --posix -E 's/1**//' 0 2 3 4 5 6 7 8 9 20 --_000_SY2PR01MB3067EE2E3074373CE2834EACBC0D2SY2PR01MB3067ausp_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
$ sed --version
sed (GNU sed) 4.9

The documentation for sed BRE syntax states:
> As a GNU extension, a postfixed regular expression can also be fo= llowed by *; for example, a** is equival= ent to a*
https://www.gnu.org/softwar= e/sed/manual/sed.html#BRE-syntax
But sed reports an error when ** is used in a BRE expression

$ seq 10 20 | sed 's/1**//'
sed: -e expression #1, char 7: Invalid preceding regular expression

and only allows this syntax when ERE syntax is enabled

$ seq 10 20 | sed -E 's/1**//'
0

2
3
4
5
6
7
8
9
20

grep, which als= o implements this GNU extension, allows ** in BRE syntax

= $ seq 10 20 | grep -o '1**'
1
11
1
1
1
1
1
1
1
1
$ seq 10 20 | grep -oE '1**'
1
11
1
1
1
1
1
1
1
1

Additionally, the documentation for the `--posix` flag states
> disable all GNU extensions.
** is = specifically documented as a GNU extension, but `--posix` doesn't disable t= he use of **

$ seq 10 20 | sed --posix -E 's/1**//'
0

2
3
4
5
6
7
8
9
20
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