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)
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