Re: [PATCH] Improve sed portability

From: Chris Ridd <chris.ridd@isode.com>
Date: Jun 12, 2008, 08:29 UTC
Message-ID: <4850DE67.703@isode.com>
In-Reply-To: <4850D45E.8000802@viscovery.net>

Johannes Sixt wrote:

Show 29 quoted lines

> Chris Ridd schrieb:
>> Johannes Sixt wrote:
>>> Chris Ridd schrieb:
>>>> @@ -73,7 +73,7 @@ resolve_relative_url ()
>>>>  module_name()
>>>>  {
>>>>      # Do we have "submodule.<something>.path = $1" defined in
>>>> .gitmodules file?
>>>> -    re=$(printf '%s' "$1" | sed -e 's/[].[^$\\*]/\\&/g')
>>>> +    re=$(printf "%s\n" "$1" | sed -e 's/[].[^$\\*]/\\&/g')
>>> You change sq into dq. Is this not dangerous? Shouldn't backslash-en be
>>> hidden from the shell so that printf can interpret it?
>> It is necessary to use double quotes. This:
>>
>>     printf '%s\n' foobar
>>
>> prints a literal \, a literal n, and no newline:
>>
>>     foobar\n
>>
>> Not desirable :-(
> 
> On both Linux and AIX 4.3 I see:
> 
> $  printf 'x\ny'; echo z
> x
> yz
> 
> The printf turns the \n into LF.

Yes, and I don't know *what* I did yesterday, but Solaris 8, 10, (every OS I mentioned before) behave the same as your test.

I did actually have my eyes tested later on yesterday :-)

> I mentioned this in the first place because I don't know what various
> shells do with \n when they see "%s\n". But one way or the other, the \n
> will be turned into LF, either by the shell or by printf. So it's not a
> big deal.

I agree.

Show 8 quoted lines

>> Of course, using a plain old:
>>
>>     echo "$1"
>>
>> should work well too. Why is printf being used here and not echo, anyway?
> 
> Because the "$1" could contain character sequences that some 'echo'
> implementations mangle.

Indeed. If $1 started with -n that might cause problems on some platforms.

Should I revise my commit to use single quotes again?

Cheers,

Chris