Re: quoting and parentheses in ExecResult?

[Knut Auvor Grythe]

On Mon, Aug 15, 2005 at 01:12:44PM +1200, Steve Wray wrote:
>>   someresult = ( ExecResult("/bin/sh -c '/bin/echo baz|/bin/sed -e 
>> \"s/^\(.*\)$/&.conf/g\"'"

Of course, I forgot closing my parentheses at the end here. I hope you
saw.

>> That way cfengine should read this as a single string all the way to the
>> next unescaped double quote (and naturally unescape the quotes inside
>> when running the command).
>
> Interestingly, this does seem to generate a parse error:
>
> cf:cfengine::./testing.cf:24: ExecResult(/command) must specify an
> absolute path
> cfengine::./testing.cf:24: Warning: Redefinition of macro
> someresult=$/&.conf/g\"'" (or perhaps missing quote)
> cf:cfengine::./testing.cf:26: syntax error
>
> I've come across this before; it almost looks as if cfengine is
> assigning a value to $(someresult) twice.

Yes, I believe it does that when it finds whitespace in the middle of
the argument. Like foo = ( bar baz ) is first set to bar, and then baz.
It is probably a side-effect of some sort of list-iteration gizmo.

>> Older versions of cfengine seem to not like quoting of the entire
>> string, but this seems to be fixed in newer versions. Upgrading might be
>> worth a shot if you're still on an older version.
>
> I'm seeing this on the version I d/l'd and compiled on Saturday... 2.1.15

Oh, okay. Then it's probably only fixed in classes, and not in groups. I
have the impression that the parsers in each section ar separated from
each other.

Maybe you can try the magic (and horrific) quotes only-syntax? Just be
sure to write a comment about what it does. I believe the syntax is
something like this:

someresult = ( "exec /bin/sh -c '/bin/echo baz|/bin/sed -e 
\"s/^\(.*\)$/&.conf/g\"'" )

If I remember correctly, "exec /" in the beginning of the string makes
it get evaluated instead of just copied. And yes, the '/' is important.
I find this syntax quite horrible, since it differs so much from the
rest of cfengine, so you should probably sheck out Marks new patch
before even considering it.

> the -c yes, but I'm not sure what you mean by 'unecessary parentheses'.
> They are required for the '&' reference to work.

No, they are required for \1 to work. '&' is always the entire match.

Like this:

  echo foo | sed 's/\(.*\)/\1.conf/'

...or like this:

  echo foo | sed 's/.*/&.conf/'

Both methods give the same result. using parentheses and \1 is often
favored, because some languages (like Perl) do all regexes in the script
a lot slower if $& is used at all (not just the regex associated with
the usage, it enables a global option turning things slooow).

The ^ and $ are also unnecessary in this case, since regex is greedy.

If you are able to write your pattern match differently, maybe you can
work around the problem this time?

--
Knut Auvor Grythe
ITEA Systemdrift