Re: [PATCH] Improve sed portability

From: Johannes Sixt <j.sixt@viscovery.net>
Date: Jun 12, 2008, 07:46 UTC
Message-ID: <4850D45E.8000802@viscovery.net>
In-Reply-To: <484FEF71.2030909@isode.com>

Chris Ridd schrieb:

Show 22 quoted lines

> 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.

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.

Show 5 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.

-- Hannes