[augeas-devel] Why does Augeas fail to handle empty files?

[David Lutterkort]

Hi Xavier,

this is indeed a bit strange. Is there any way you could send your lens,
maybe together with some test cases along the lines of 'test lns get "" = *
(* Stuff totally blows up here unexpectedly *)' or similar ?

David


On Fri, Feb 12, 2016 at 3:49 AM, Mol, Xavier (SCC) <xavier.mol at kit.edu>
wrote:

> Hi Raphaël.
>
>
>
> > An empty file contains "\n", not "".
>
> So what you are saying is, that Augeas doesn't understand the concept of
> empty files? It will always interpret them as beeing filled with an empty
> line (which translates into an empty tree node)?
>
>
>
> Even though, that doesn't explain my question what the difference between
>
>
>
> let lns = properties? . ( filler | domain )*
>
>
>
> and
>
>
>
> let lns = ( properties? . ( filler | domain )* )?
>
>
>
> is.
>
>
>
> Ciao,
>
> Xavier.
>
>
>
>
>
>
>
> *From:* Raphaël Pinson [mailto:raphael.pinson at camptocamp.com]
> *Sent:* Friday, February 12, 2016 11:00 AM
> *To:* Mol, Xavier (SCC)
> *Cc:* augeas-devel at redhat.com
> *Subject:* Re: [augeas-devel] Why does Augeas fail to handle empty files?
>
>
>
>
>
>
>
> On Fri, Feb 12, 2016 at 10:57 AM, Mol, Xavier (SCC) <xavier.mol at kit.edu>
> wrote:
>
> Hi again.
>
>
>
> > let lns = ( properties? . ( filler | domain )* )?
>
> One more note on this: After I have changed this line, augparse compains
> that a very complicated regular expression "matches the empty word", which
> actually is the point of the exercise.
>
>
>
> It shouldn't be. An empty file contains "\n", not "".
>
>
>
>
>
> Raphaël
>
>
>
>
>
>
>
>
>
> *From:* augeas-devel-bounces at redhat.com [mailto:
> augeas-devel-bounces at redhat.com] *On Behalf Of *Mol, Xavier (SCC)
> *Sent:* Friday, February 12, 2016 9:13 AM
> *To:* augeas-devel at redhat.com
> *Subject:* [augeas-devel] Why does Augeas fail to handle empty files?
>
>
>
> Hello Augeas experts,
>
>
>
> this issue was mentioned in a previous mail thread on this list (see
> attached final mail) and I've run into it again: Augeas seems to be quite
> strict about empty files (as opposed to non-existing files).
>
>
>
> I have a lens defined like this 'let lns = properties? . ( filler | domain
> )*'. The actual meaning of the sub-lenses is not important right now, since
> per regular expression this should successfully match the void. It indeed
> does create new files, but it fails to update empty files and this is the
> error message I get:
>
>
>
> """
>
> [root ~]# >/etc/dcache/layouts/f01-151-109-e.conf
>
> [root ~]# augtool
>
> augtool> print /files/etc/dcache/layouts/f01-151-109-e.conf
>
> /files/etc/dcache/layouts/f01-151-109-e.conf
>
> augtool> set
> /files/etc/dcache/layouts/f01-151-109-e.conf/properties/dcache.java.memory.heap
> 2g
>
> augtool> print /files/etc/dcache/layouts/f01-151-109-e.conf
>
> /files/etc/dcache/layouts/f01-151-109-e.conf
>
> /files/etc/dcache/layouts/f01-151-109-e.conf/properties
>
> /files/etc/dcache/layouts/f01-151-109-e.conf/properties/dcache.java.memory.heap
> = "2g"
>
> augtool> save
>
> error: Failed to execute command
>
> saving failed (run 'errors' for details)
>
> augtool> errors
>
> Error in /etc/dcache/layouts/f01-151-109-e.conf (put_failed)
>
>   Failed to match
>
>         { /properties/ }?
>
> (    { /#comment/ = /[^\001-\004\t\n\r ][^\001-\004\n]*[^\001-\004\t\n\r
> ]|[^\001-\004\t\n\r ]/ }
>
>       | { }
>
>       | { /domain/ = /[$.0-9A-Z_a-{}-]+/ })*
>
>   with tree
>
>     {  } { "properties" }
>
>   Lens: /var/lib/puppet/lib/augeas/lenses/dcachelayout.aug:29.12-.46:
>
> """
>
>
>
> For some reason, there is an empty node before the properties node, which
> failes the put direction. For that the lens needs to be written like…
>
>
>
> let lns = ( properties? . ( filler | domain )* )?
>
>
>
> As far as regular expressions go, there is no effective change here,
> right? Yet for Augeas this clearly seems to make a difference. Can someone
> maybe explain this to me?
>
>
>
> Thank you for your time,
>
> Xavier.
>
>
>
>
>
> ****
>
> Karlsruher Institute of Technology (KIT)
>
> Steinbuch Centre for Computing (SCC)
>
>
>
> B. Sc. Xavier Mol
>
> GridKa Storage Administrator and Support Manager
>
>
>
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>
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>
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>
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>
> Email: xavier.mol at kit.edu
>
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>
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> Large-scale Research Center of the Helmholtz Association
>
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>
> ****
>
>
>
>
>
>
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> --
>
> Raphaël Pinson
>
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>
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>
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