Re: [Xen-devel] [PATCH 2 of 5 V3] tools/hotplug: Remus network buffering setup scripts

[Shriram Rajagopalan <rshriram@xxxxxxxxx>]

On Thu, Oct 31, 2013 at 5:25 PM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:

> This was to just make sure that the IFB variable was supplied as part

> of the environment..
> Just like the two checks on top of this script..
> "
> : ${vifname?}
> : ${XENBUS_PATH?}
> "

Do these result in useful error reporting to the end user?

It displays a message "<script name>:lineno: vifname: parameter not set or null"

on stderr.

 

Bearing in
mind that the end user might be using libxl but not xl and therefore not
see stdout/err (which might be going into some daemon's log file).

These parameters are supposed to be set by libxl before fork+exec-ing the script.

And their values are not obtained from the user or the command line. They are

generated inside libxl, and checked for non-null status.  So I dont think we need

to worry about libxl not being able to see the error.

 

Also, either I'm missing it or the bash manpage only documents
${parameter:?} and not ${parameter?}. Are both actually valid?

You are right. The man page documents only the ${parameter:?} format,

although the "${parameter?}" also seems to work for me. I will stick to the

documented format.

 

Ian.

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