Re: regex quirks

got it...used the old but gold replace or add stuff...

bundle edit_line itsv_replace_or_add_cron_line ( pattern, line )
# @brief modify lines matching a regular expression eg. ".*\/usr\/bin\/nmon 
-F \/var\/log\/nmon.*1.*"
# @param pattern The pattern that should be replaced The pattern must match 
the whole line (it is automatically anchored to the start and end of the 
line) to
# avoid ambiguity.
# @param The line with which to replace matches of pattern
{

  vars:

  "cline" string => canonify("$(line)");
  "eline" string => escape("$(line)");

  replace_patterns:

    "^(?!$(eline)$)$(pattern)$"
        comment => "replace a pattern",
        replace_with => value("$(line)"),
        classes => scoped_classes_generic("bundle", "replace_$(cline)");

  insert_lines:

      "$(line)"
          ifvarclass => "replace_$(cline)_reached";

#   delete_lines:
#
#      "^($(_find))$";
#
#   insert_lines:
#
#     "$(_replace)";


}


On Friday, August 6, 2021 at 8:23:14 AM UTC+2 Xander Cage wrote:

> when i negate the regex the info message is gone, but no edits are 
> done...causality dilemma. 
>
> bundle edit_line itsv_modify_cron_line ( _find, _replace )
> # @brief modify lines matching a regular expression eg. 
> ".*\/usr\/bin\/nmon -F \/var\/log\/nmon.*1.*"
>
> # @param _find The regular expression that the lines need to match
> # @param _replace String to substitute `_find` with
> {
>
>   replace_patterns:
>
>    "^(?!$(_find))$"
>
>      replace_with => value("$(_replace)");
>
> #   delete_lines:
> #
> #      "^($(_find))$";
> #
> #   insert_lines:
> #
> #     "$(_replace)";
>
>
> }
>
>
> On Tuesday, August 3, 2021 at 1:22:49 PM UTC+2 [email protected] 
> wrote:
>
>> On Wed, 2021-07-28 at 07:29 -0700, Xander Cage wrote: 
>> > 
>> > hey, 
>> > 
>> > i'm toying  around in making a bundle for crontab editing (add, 
>> > modify, remove) and regex is 
>> > beginning to bite me. 
>> > 
>> > i got an "informational" message that my pattern matching skills are 
>> > downlevel. 
>> > 
>> > /var/cfengine/bin/cf-agent -KI -f ./nmon_cron_test.cf 
>> >     info: Promised replacement '0 0 * * * /usr/bin/nmon -F 
>> > /var/log/nmon/`hostname`_`date +'\%y\%m\%d_\%H\%M'`.nmon -s 300 -c 
>> > 288 1>/dev/null 2>/dev/null' for pattern '^.*/usr/bin/nmon -F.*$' is 
>> > not properly convergent while editing '/var/spool/cron/crontabs/root' 
>> >     info: Because the regular expression '^.*/usr/bin/nmon -F.*$' 
>> > still matches the end-state replacement string '0 0 * * * 
>> > /usr/bin/nmon -F /var/log/nmon/`hostname`_`date 
>> > +'\%y\%m\%d_\%H\%M'`.nmon -s 300 -c 288 1>/dev/null 2>/dev/null' 
>>
>> The 'info' message explains what the problem is -- the anchor regular 
>> expression matches the replacement string. That means the promise 
>> doesn't converge -- it will make a change every time it is evaluated. 
>> That's generally considered a bad pattern in CFEngine (and any engine 
>> based on state specification instead of action specification). 
>>
>> You can ignore the message or, ideally, change the regex to only match 
>> the undesired state. 
>>
>> Thanks. 
>>
>> -- 
>> Vratislav 
>>
>

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