GNU bug report logs - #20796
[PATCH] Document behavior of sed -i -

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Stanislav Brabec <sbrabec <at> suse.com>
Subject: bug#20796: closed (Re: bug#20796: [PATCH] Document behavior of
 sed -i -)
Date: Tue, 23 Jun 2015 16:12:03 +0000

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Your bug report

#20796: [PATCH] Document behavior of sed -i -

which was filed against the sed package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 20796 <at> debbugs.gnu.org.

-- 
20796: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=20796
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Jim Meyering <jim <at> meyering.net>
To: Stanislav Brabec <sbrabec <at> suse.com>
Cc: 20796-done <at> debbugs.gnu.org
Subject: Re: bug#20796: [PATCH] Document behavior of sed -i -
Date: Tue, 23 Jun 2015 09:11:10 -0700

On Mon, Jun 22, 2015 at 7:06 AM, Jim Meyering <jim <at> meyering.net> wrote:
> On Mon, Jun 22, 2015 at 6:43 AM, Stanislav Brabec <sbrabec <at> suse.com> wrote:
>> Jim Meyering wrote:
>>
>>> However, rather than documenting this surprising behavior,
>>> I propose to remove the anomaly altogether with the attached patch.
>>> Does anyone see a reason to retain the behavior of treating "-"
>>> like "./-"?
>>>
>> The reason is simple: "sed -i" makes no sense on stdin, so the special
>> handling od "-" is disabled.
>>
>> We can either ignore "-i" for stdin, or report error:
>> "Editing standard input in place is an undefined operation."
>
> Ignoring a fundamental user-specified option like -i is not an option,
> so I chose the latter: to make this nonsensical usage evoke
> a diagnostic:
>
>   $ sed -i s/a/b/ -
>   sed: couldn't edit -: is a terminal
>
> I chose to use the same diagnostic that was already printed for
> a case like "sed -i s/a/b/ /dev/stdin".  It feels slightly better to
> include the name of the offending device.

I've pushed that change.

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From: Stanislav Brabec <sbrabec <at> suse.com>
To: bug-sed <at> gnu.org
Subject: [PATCH] Document behavior of sed -i -
Date: Fri, 12 Jun 2015 17:32:50 +0200

"sed -i -" does not fail, but it also does not do what one would expect.
Document it, as it could have security implications:

Example:
The sed command below looks broken, but it is executed and succeeds:

ln -s /etc/passwd -- -
echo root | sed -i --follow-symlinks s/root/parrot/ -

Signed-off-by: Stanislav Brabec <sbrabec <at> suse.cz>
---
 doc/sed-in.texi | 1 +
 1 file changed, 1 insertion(+)

diff --git a/doc/sed-in.texi b/doc/sed-in.texi
index 0e10cde..c8f1289 100644
--- a/doc/sed-in.texi
+++ b/doc/sed-in.texi
@@ -180,6 +180,7 @@ sed OPTIONS... [SCRIPT] [INPUTFILE...]
 @end example
 
 If you do not specify @var{INPUTFILE}, or if @var{INPUTFILE} is @file{-},
+and @option{-i} is not used,
 @command{sed} filters the contents of the standard input.  The @var{script}
 is actually the first non-option parameter, which @command{sed} specially
 considers a script and not an input file if (and only if) none of the
-- 
2.4.2

-- 
Best Regards / S pozdravem,

Stanislav Brabec
software developer
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