On Tue, Mar 02, 2010 at 10:58:35AM -0500, Daniel V Klein wrote:
>Speaking just for myself (and not cfengine today), I think this is a good idea.
That's good to hear--there's at least one other crazy person here! :-)
>As long as you're at it, you probably want a tolower() and toupper() function.
And, left(), right(), substr(), length(), sprintf(), s///, and others.
>You can get "ignore case" on regular expression matching with PCRE '(?i)',
>but converting to lower or to upper on output is harder (and if you want
>convergence, you DON'T want what Perl does... :-)
There are lots of things where I don't want what Perl does. :) But
along the lines of convergence, I don't see that a regreplace type of
function is any more or less convergent than splitstring() or join().
Both of those existing functions take existing variables and create a
new variable while leaving the original(s) untouched.
>Also, in your model, regreplace needs a 4th argument - "first" or "all", to
>give you the equivalent of /g substitution. While "first" can be a bad
>thing, there is already precendent for that in Cfengine in the replacement of
>lines in files...
Agreed, a first/all argument is needed.
>
>-Dan
>
>> On Tue, Mar 02, 2010 at 08:33:15AM -0500, nwat...@symcor.com wrote:
>> >I don't think there is a function at present for string search a replace
>> >actions out side of file editing. Perhaps look at it from a higher level.
>> > Why is string manipulation needed?
>>
>> There are two reasons, one specific, and one general.
>>
>> The specific reason is that I am trying to build a somewhat more robust
>> template library (which if I ever get to work, I will post to the list).
>>
>> To do this, I am trying to convert a file from the form of
>> "/some/path/to/file" into something like
>> "/path/to/repo/_some_path_to_file".
>>
>> This is trivial with two regexes. Using quasi-cfengine notation, and
>> a hypothetical regreplace(string,find,replace) function, something like
>> this would work:
>>
>> vars:
>> "orig" = "/some/path/to/file";
>> "new" = regreplace(
>> regreplace("${orig}", "/", "_" ),
>> "^",
>> "/path/to/repo"
>> );
>>
>>
>>
>> The general reason is that string search and replace is a very useful
>> tool. It doesn't really matter the what the specific problem actually
>> is, since this is a more general issue. A good tool is useful in lots
>> of different situations, including those in which it was not originally
>> intended.
>>
>> There have been several occasions where a simple string replacement would
>> make certain promises simpler, but I have attempted to work around them.
>> But having to shell out and make two calls to outside binaries--one
>> of them being echo!--just to do a simple string manipulation seems
>> counter-productive, inefficient, and much more error prone (especially
>> due to the hazards of shell quoting).
>>
>> Here's another example, albeit slightly contrived. You have a system
>> where you want to start hashing user home directories in the form of
>> "jbecker -> /home/j/jbecker" (for example). Based on some
>> list of users, there is a set of promises to ensure that the accounts
>> exist, including calling 'useradd'. Having a short set of promises to
>> convert the string "jbecker" into "/home/j/jbecker" is fairly easy using
>> a search and replace function. I can envision a situation where
>> cfengine could actually handle the migration of existing "unhashed" user
>> home directories to "hashed" ones, but only if it supports better string
>> handling routines.
>>
>> Of course, one can always just hand off a username to a Perl script as
>> well.
>>
>> I really want is a general solution (which is why I did not simply ask
>> how to munge a path). Once I--and everyone else--has that, the
>> specifics should be simple. :)
>>
>>
>>
>> --
>> Jesse Becker
>> NHGRI Linux support (Digicon Contractor)
>> _______________________________________________
>> Help-cfengine mailing list
>> Help-cfengine@cfengine.org
>> https://cfengine.org/mailman/listinfo/help-cfengine
--
Jesse Becker
NHGRI Linux support (Digicon Contractor)
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