Re: typeset -p output gives shows variables which can't be read back in

[Rocky Bernstein <rocky@xxxxxxx>]

Thanks for the suggestions. I had been parsing typeset -p output by
splitting words and using a regexp match. Now, thanks to your suggestion, I
use the parameters module.

As for the typeset -T and typeset -p not showing -T associations, I think
that's a misfeature. What's shown now are array assignments and you don't
reliably know what goes with what. Much better would be to show the
association. That is if I run:
   typeset -T foo FOO
then typeset -T should echo that among the other -T possibilities. I can
always get the array and scalar values if I want. But getting the other
information, as you say, is not easy if possible at all.

Should I look into providing a patch for this?

Saving an environment for reloading into another session, whether nested or
not, might be useful in other contexts. Possibly the code you or I have in
zshdb could be turned into a function and put inside the parameter module?


On Sun, Feb 27, 2011 at 4:01 PM, Bart Schaefer <schaefer@xxxxxxxxxxxxxxxx>wrote:

> On Feb 27,  6:44am, Rocky Bernstein wrote:
> }
> } A little bit of context of why I am doing this. Recently in the zsh
> } debugger I've added the ability to go into a nested zsh, and often one
> } wants the existing environment of the debugged program preserved in
> } this nested zsh.
>
> You're kind of doomed here from the start.  If the debugger is inside
> a shell function, for example, you're never going to get scoping back.
>

Not true in a couple of ways. First even if you changing values doesn't
persist, it is
useful to be able to see the values.

What I'm thinking of now is adding a function save_var which takes the name
of
a variable one wants to persist. In an at_exit hook (or whatever the
equivalent is on zsh),
then those variables are written out to a file similar to what was done on
entry to get all of those
variables set.

If there is something like a tie function like there is in Perl or a
discipline function on a varaible
like ksh, that might be used, but this would be on a per-variable basis.

Other comments are in line below.


>
> } I would like to save to a file shell variables so that I can run a
> } nested zsh and then read these back in.  It is becoming a bit of a
> } challenge because this in the output:
> }
> } typeset -i10 -r !=0
>
> Hm, I'm a bit surprised the '!' isn't quoted there; but the real issue
> is that you get "not an identifier" or the like for a number of those,
> and "can't change type" for ones that come from zsh/parameter, plus a
> few "read-only variable" complaints.
>
> } typeset -ar '*'
>
> Hmm, strange.  That one does NOT give "not an identifier" ...
>
> } *=()
>
> ... but that of course bombs with a globbing error.
>

So although I can see how this might be useful as an explanation, I think
it would be nice if there were some simple way (i.e. something in the
typeset -p command)
to filter out those things that can't be source'd back in.


>
> } Failing a better solution, I think what I'll have to do is store IFS=''
> } typeset -p into an array and check each item of the array.
>
> The zsh/parameter module $parameters hash already tells you nearly all
> you need to know.  Something like this:
>
>    () {
>      local param type
>      for param type in "${(kv@)parameters}"
>      do
>        case "$type" in
>        (*local*) continue;;   # Skip loop variables
>        (*export*) continue;;  # No need to dump/restore if exported?
>        (*special*) continue;; # Maintained by the shell
>        (*readonly*) continue;;
>        (*) typeset -p "$param";;
>        esac
>      done
>    }
>
> You can avoid zsh/parameter by parsing the output of "typeset +m +":
>
>    () {
>      local param type description
>      typeset +m + | while read -A description
>      do
>        param="${description[-1]}"
>        description[-1]=()
>        if (( ${#description} ))
>        then type="${description[*]}"
>        else type=scalar
>        fi
>        case "$type" in
>        (*local*) continue;;   # Skip loop variables
>        (*export*) continue;;  # No need to dump/restore if exported?
>        (*readonly*) continue;;
>        (*) typeset -p "$param";;
>        esac
>      done
>    }
>

Thanks again. I have modified the code to do something like this. Note
however I don't want to
skip local variables, because in a debugger that's one of the important
things we want to examine.

And read-only variables I want to  skip only if they are already set. That's
why I had that
typeset -p $var >/dev/null 2>&1 ||  prefix in the code before. (I had
erroneously used && instead of ||
and and a stray character in there.)

But all of this is easily fixed.


> However, that doesn't let you catch "special" parameters, though you
> can still filter the readonly subset.
>
> Note both of these techniques still miss things like:
>
>    typeset -T foo FOO
>
> I.e., there's no way to discover by examination that an array and scalar
> have been tied together.
>
> } But then we come to the typeset -ar '*' line which I guess flows onto the
> } next line.
>
> Not exactly "flows", but for arrays and associative arrays (hashes) the
> value can't be supplied in the typeset command, so an assignment line is
> needed.
>

Yes, I meant that the semantic description of the variable flows into the
next line, not that there was one
statement split on two lines.  I often write these two statements on one
like with a semicolon
in between.

But while we are being precise, let me point out that it is wrong to say
that a local variable is a
"loop" variable as you suggest in the code above.


> Also you may have to be careful with the order of assignments when you
> read the file back in.  Some assignments to special variables (like to
> the "options" hash) might change shell behavior in unexpected ways.
>

Ok. Thanks, I will keep that in mind. Right now, I'm skipping the special
variables as you had in your code.

Should I need them and I discover that there is an ordering problem, I think
it is a simple matter to put these
in a list which gets run in list order after doing other variables first