[augeas-devel] Dealing with empty values

[Erinn Looney-Triggs]

On 11/18/2010 10:10 AM, Raphaël Pinson wrote:
> Hi Erinn,
>
> On Thu, Nov 18, 2010 at 5:55 PM, Erinn Looney-Triggs
> <erinn.looneytriggs at gmail.com <mailto:erinn.looneytriggs at gmail.com>>
> wrote:
>
>     Searched around to try to find an answer to this but can't find
>     anything
>     yet. I am writing a lense for /etc/default/useradd, pretty simple file
>     really key value separated by =. Here is the lense:
>     module Useradd =
>     autoload xfm
>
>     let eq = Util.del_str "="
>
>     let record =
>      let value = store /[^ \t\n]+([ \t]+[^ \t\n]+)*/ in
>      [ key Rx.word . eq . value . Util.eol ]
>
>     let lns = (record | Util.comment | Util.empty) *
>
>     let filter = incl "/etc/defaults/useradd" . Util.stdexcl
>
>     let xfm = transform lns filter
>
>     Here are the tests:
>
>     module Test_useradd =
>
>     let record = "GROUP=100
>     HOME=/home
>     INACTIVE=-1
>     EXPIRE=
>     SHELL=/bin/bash
>     SKEL=/etc/skel
>     CREATE_MAIL_SPOOL=yes
>     "
>
>     test Useradd.lns get record =
>        { "GROUP" = "100" }
>        { "HOME" = "/home" }
>        { "INACTIVE" = "-1" }
>        { "EXPIRE" = "" }
>        { "SHELL" = "/bin/bash" }
>        { "SKEL" = "/etc/skel" }
>        { "CREATE_MAIL_SPOOL" = "yes" }
>
>     let comment ="# useradd defaults file
>     "
>
>     test Useradd.lns get comment =
>      {"#comment" = "useradd defaults file"}
>
>     The problem is the EXPIRE= line. now I know that as my match currently
>     stands it is looking for a value not delimited by a \n or a space. So
>     clearly that isn't going to work but I can't figure out what will.
>     Myabe
>     I am making this harder than it needs to be but storing \n as a value
>     works, sort of except that you now have a newline as a value. I guess
>     what I am looking fro is to replace the newline with "" as the value.
>     Del would seem to be right for that, but I can't seem to store a del.
>     Any help would be appreciated as I am pretty new to this.
>
>
>
> I'd say the simplest way to do that would be to make value optional:
>
> let record =
>  let value = store /[^ \t\n]+([ \t]+[^ \t\n]+)*/ in
>  [ key Rx.word . eq . value? . Util.eol ]
>
> and then:
>
> test Useradd.lns get record =                           
>    { "GROUP" = "100" }
>    { "HOME" = "/home" }       
>    { "INACTIVE" = "-1" }                                              
>        
>    { "EXPIRE" }                                                      
>         
>    { "SHELL" = "/bin/bash" }                                          
>        
>    { "SKEL" = "/etc/skel" }                                          
>         
>    { "CREATE_MAIL_SPOOL" = "yes" }     
>
>
> Since "=" is mandatory in your file, you can consider that an empty
> value can be represented by a flag.
>
>
> Raphaël
>
>  

Great thanks for that, solves the issue very nicely. I will be opening
up another bug with the lens and tests here in a few minutes.

Thanks again,
-Erinn


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