Re: [Xen-devel] [PATCH 7/7] tools/hotplug: add wrapper to start xenstored

[Olaf Hering <olaf@xxxxxxxxx>]

On Thu, Sep 10, Ian Jackson wrote:

> Wei Liu writes ("Re: [Xen-devel] [PATCH 7/7] tools/hotplug: add wrapper to 
> start xenstored"):
> > On Thu, Sep 10, 2015 at 03:19:35PM +0100, George Dunlap wrote:
> > > ExecStart=/usr/bin/env $XENSTORED --no-fork $XENSTORED_ARGS
> > 
> > And the difference between these two approaches is /usr/bin/env
> > preserves envars while sh -c doesn't?
> 
> Who interpolates $XENSTORED and $XENSTORED_ARGS here ?  Was systemd
> doing that all along ?
> If XENSTORED_ARGS contains spaces, what happens ?

Yes, its described in the docs. Also $var vs. ${var} is slightly
different:

http://www.freedesktop.org/software/systemd/man/systemd.service.html
...
Command lines
...
Basic environment variable substitution is supported. Use "${FOO}" as
part of a word, or as a word of its own, on the command line, in which
case it will be replaced by the value of the environment variable
including all whitespace it contains, resulting in a single argument.
Use "$FOO" as a separate word on the command line, in which case it will
be replaced by the value of the environment variable split at whitespace
resulting in zero or more arguments. For this type of expansion, quotes
and respected when splitting into words, and afterwards removed.
...


Olaf

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