Re: [ptxdist] [PATCH 2/3] rc-once: Use readlink to check where /system-update points to.

[Michael Olbrich <m.olbrich@pengutronix.de>]

On Tue, Jun 06, 2017 at 06:25:09PM +0200, Uwe Kleine-König wrote:
> On Tue, Jun 06, 2017 at 06:00:51PM +0200, Michael Olbrich wrote:
> > On Tue, Jun 06, 2017 at 05:28:48PM +0200, Gavin Schenk wrote:
> > > rc-once ist based on systemd offline update mechanism.
> > > https://www.freedesktop.org/software/systemd/man/systemd.offline-updates
> > > 
> > > To make it possible to have multiple update services beside rc-once the
> > > script should check where the link /system-update points to.
> > > 
> > > rc-once will only run if the link points to etc/rc-once.d or
> > > /etc/rc-once.d.
> > > 
> > > Signed-off-by: Gavin Schenk <g.schenk@eckelmann.de>
> > > ---
> > >  projectroot/usr/lib/init/rc-once.sh | 5 +++++
> > >  rules/rc-once.in                    | 3 +++
> > >  2 files changed, 8 insertions(+)
> > > 
> > > diff --git a/projectroot/usr/lib/init/rc-once.sh b/projectroot/usr/lib/init/rc-once.sh
> > > index 8689a32bc..d225ad5c2 100644
> > > --- a/projectroot/usr/lib/init/rc-once.sh
> > > +++ b/projectroot/usr/lib/init/rc-once.sh
> > > @@ -6,6 +6,11 @@ STAMP="$DONE_DIR/rc-once"
> > >  
> > >  run_rc_once() {
> > >  	failed=0
> > > +	UPDATE_TARGET=$(readlink -f /system-update)
> > 
> > This needs quotes in case the link target contains spaces.
> 
> I think that's wrong. It only needs quoting when being used:
> 
> 	$ cat test.sh 
> 	#!/bin/sh
> 
> 	tmpdir=$(mktemp -d)
> 
> 	touch "$tmpdir/file with	spaces";
> 
> 	FILE=$(ls $tmpdir)
> 
> 	echo "$FILE"
> 
> 	rm -rf $tmpdir
> 
> 	$ bash test.sh  | hexdump -C
> 	00000000  66 69 6c 65 20 77 69 74  68 09 73 70 61 63 65 73  |file with.spaces|
> 	00000010  0a                                                |.|
> 	00000011
> 
> That being said, quotes don't hurt either.

This is strange. I see the same thing, but the bash man-page says:
"If the substitution appears within double quotes, word splitting and
pathname expansion are not performed on the results."
So I'd assume, that word splitting and pathname expansion are performed if
no quotes are used, but that doesn't seem to happen.

Michael

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