[augeas-devel] How to insert empty nodes in Augeas trees?

Tue Dec 22 15:36:01 UTC 2015

Hi Raphael.

> How about something like this:

>    let token = (mapping | pwdrecord | record_nobreak)* . (mapping | pwdrecord | record_nobreak)

How is that different from this token definition?

let token = (mapping | pwdrecord | record_nobreak)+

And how does record_nobreak look for you? If it is record as I have defined it without break at its end, then I don't think that will work. Evectively record_nobreak then assumes that all lines/nodes, that are not matched by either Util.empty, Util.comment, mapping or pwdrecord belong to a record_nobreak node. Did I understand you right?

Ciao,

Xavier.

From: Raphaël Pinson [mailto:raphael.pinson at camptocamp.com] 
Sent: Tuesday, December 22, 2015 4:28 PM
To: Mol, Xavier (SCC)
Cc: augeas-devel at redhat.com
Subject: Re: [augeas-devel] How to insert empty nodes in Augeas trees?

On Tue, Dec 22, 2015 at 2:32 PM, Mol, Xavier (SCC) <xavier.mol at kit.edu> wrote:

Hi Raphael,

a concrete example snippet might look similar to what I've done with the unit tests (see test_kpwd.aug in attachements). The important lens in this context is called 'record' in kpwd.aug. That lens has to consume an unknown number of lines from a configuration file, until it encounters a blank line. At first I was looking for Util.empty, which worked fine, until I wanted to code a put unit test, hence the inquery of how to include empty nodes in an Augeas tree. After all, the better solution was to look for two line breaks (Util.eol . del "\n" "\n"), which doesn't generate, nor require empty nodes in the Augeas tree.

Then you brought up that we might encounter the end of a file, instead of line breaks, which I don't know how to handle with Augeas parsing. Because of that very issue, all of my custom lenses require each configuration file to end on a new line. Simply making the eol optional causes a lot of ambiguities and eof doesn't have a string representation, so there is no regular expression for matching it explicitly. Unless you know something that I don't. J

How about something like this:

    let token = (mapping | pwdrecord | record_nobreak)* . (mapping | pwdrecord | record_nobreak)

Cheers,

Raphaël

From: Raphaël Pinson [mailto:raphael.pinson at camptocamp.com] 
Sent: Tuesday, December 22, 2015 2:12 PM

To: Mol, Xavier (SCC)
Cc: augeas-devel at redhat.com
Subject: Re: [augeas-devel] How to insert empty nodes in Augeas trees?

Do you have concrete examples of what you're trying to achieve, so I understand better?

On Tue, Dec 22, 2015 at 2:05 PM, Mol, Xavier (SCC) <xavier.mol at kit.edu> wrote:

Hi Raphael,

no, I need an empty line after Uitl.eol, before any other text. But you bring up an interesting point, that my lens doesn't recognize the end of a file, which could be accepted all the same, without requiring an actual empty line. But how can I match the end of a file?

Ciao,

Xavier.

From: Raphaël Pinson [mailto:raphael.pinson at camptocamp.com] 
Sent: Tuesday, December 22, 2015 1:31 PM

To: Mol, Xavier (SCC)
Cc: augeas-devel at redhat.com
Subject: Re: [augeas-devel] How to insert empty nodes in Augeas trees?

It's common to end every line with a Util.eol, which defaults to a newline. Or do you mean that you need an empty line at the end of the file?

Raphaël

On Tue, Dec 22, 2015 at 12:58 PM, Mol, Xavier (SCC) <xavier.mol at kit.edu> wrote:

Hi Raphael, all,

some more finding about this…

Neither 'touch', nor 'rename' can be used during a put unit test. Also, relying on Augeas users to do this just to insert a line break, which is required for a valid configuration file, is ugly and error prone. This workaround still may be used to add additional empty lines to a configuration file just to improve readability (where they don't break anything), so still a useful lesson. Though for my custom lens, I have decided to look for and create empty lines by default, as with any string literal. This way, the Augeas tree doesn't need to feature empty nodes and empty lines will be added in put direction automatically.

Thank you again for your time,

Xavier.

From: augeas-devel-bounces at redhat.com [mailto:augeas-devel-bounces at redhat.com] On Behalf Of Mol, Xavier (SCC)
Sent: Tuesday, December 22, 2015 10:27 AM
To: Raphaël Pinson

Cc: augeas-devel at redhat.com
Subject: Re: [augeas-devel] How to insert empty nodes in Augeas trees?

Hi Raphael,

thank you again for your quick and helpful reply!

Ciao,

Xavier.

From: Raphaël Pinson [mailto:raphael.pinson at camptocamp.com] 
Sent: Tuesday, December 22, 2015 10:25 AM
To: Mol, Xavier (SCC)
Cc: augeas-devel at redhat.com
Subject: Re: [augeas-devel] How to insert empty nodes in Augeas trees?

Hello Xavier,

I was going to say that was not possible, but I actually (to my great surprise) found a way to do it:

    augtool> touch /files/etc/fstab/01

    augtool> rename /files/etc/fstab/01 ""

    rename : /files/etc/fstab/01 to  1

    augtool> save

    Saved 1 file(s)

Just added an empty line at the end of /etc/fstab

Cheers,

Raphaël

On Tue, Dec 22, 2015 at 10:06 AM, Mol, Xavier (SCC) <xavier.mol at kit.edu> wrote:

Hello Augeas experts,

is there a way to insert empty nodes in an Augeas tree? I've made a lens, that expects an empty line as last part (Util.empty), which works fine with existing files. However, when inserting a new node in the tree with that lens, the closing empty line is missing. Do I need to have a labelled node in the tree without value or children, that simply puts an empty line in the resulting string instead?

Thank you for your time,
Xavier.

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Raphaël Pinson

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+33 458 482 013

Camptocamp France
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-- 

Raphaël Pinson

Infrastructure Developer & Training Leader

+33 458 482 013

Camptocamp France
Savoie Technolac
BP 352
48, avenue du Lac du Bourget
73372 Le Bourget du Lac, Cedex
www.camptocamp.com

-- 

Raphaël Pinson

Infrastructure Developer & Training Leader

+33 458 482 013

Camptocamp France
Savoie Technolac
BP 352
48, avenue du Lac du Bourget
73372 Le Bourget du Lac, Cedex
www.camptocamp.com

-- 

Raphaël Pinson

Infrastructure Developer & Training Leader

+33 458 482 013

Camptocamp France
Savoie Technolac
BP 352
48, avenue du Lac du Bourget
73372 Le Bourget du Lac, Cedex
www.camptocamp.com

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