Re: [BUGS] test failure in t4014-format-patch.sh with master

From: Björn Steinbrink <b.steinbrink@gmx.de>
Date: Apr 17, 2008, 16:03 UTC
Message-ID: <20080417160327.GA13462@atjola.homenet>
In-Reply-To: <alpine.LFD.1.00.0804170841270.2879@woody.linux-foundation.org>

On 2008.04.17 08:44:07 -0700, Linus Torvalds wrote:

Show 22 quoted lines

> 
> 
> On Thu, 17 Apr 2008, Björn Steinbrink wrote:
> > 
> > Debian has its own dash which is supposed to be a lightweight
> > alternative to bash and "for checking POSIX compliance of scripts"
> > (quote from the packages description). I don't happen to know off-hand
> > whether POSIX says that echo should default to -e, but dash seems to do
> > that:
> > 
> > $ dash
> > $ a="hello\nhi"
> > $ echo $a
> > hello
> > hi
> 
> Ahh. So that "echo" should just be replaced with a 'printf "%s\n"' 
> instead? 
> 
> We have a _lot_ of "echo"s though. I suspect the only ones we'd ever catch 
> are the ones explicitly tested for. I suspect that the dash echo is just 
> broken.

Wow, seems that "echo" in itself is "broken". According to POSIX[1] backslashes induce implementation defined behaviour, and there seem to be two historic versions of echo, one that knows about -n and one that interprets escape sequences. So echo is totally non-portable unless you avoid -n as well as backslashes. Ouch.

The POSIX docs, as well as random Google results, indeed recommend to use printf instead. But that switch seems painful as well...

Björn

[1] http://www.opengroup.org/onlinepubs/009695399/utilities/echo.html