[9fans] debugging rc

[9fans] debugging rc

[Rudolf Sykora]

Hello all,

yesterday I wanted to try out rc-httpd on p9p&linux. There, in an rc
script was sth along the following lines:

file = aaanamebb
a = name
if(~ $file *$a*) echo y

and the script returned

rc: null list in concatenation

I wrote to the author that I believe he should have written *$a^* in
the condition.

Nonetheless I have 2 questions:
1) if *$a* is left there, is the meaning really: whatever_non_blank +
contents of $a + literal * ?
2) it took me some time to localize where the problem was since the
only output of the script was what I wrote above; so I went commenting
& uncommenting... Is there any better way? Can rc be told to give some
more helpful info?

Thanks
Ruda

Re: [9fans] debugging rc

[dexen deVries]

On Tuesday 05 of July 2011 09:31:43 Rudolf Sykora wrote:
> (...) 
> Is there any better way? Can rc be told to give some
> more helpful info?

there are:
flag x +
flag r +

the output produced by r + is somewhat strange, but may be good enough. In your case, it shows difference between *$a* and *$a^*:

the former is:

Xdol (a*) () ()
Xmark () ()
Xword () () ()
Xconc (*) () ()
rc: null list in concatenation


(guess `Xdol (a*)' means `dereference variable a*' (preasumably empty), which is  in turn Xconc()atenated with literal `*' and thus the error)

the later is 

Xdol (a) () () (*) ()
Xmark (name) () (*) ()
Xword () (name) () (*) ()
Xconc (*) (name) () (*) ()
Xconc (*name) (*) ()




-- 
dexen deVries

[[[↓][→]]]

For example, if the first thing in the file is:
   <?kzy irefvba="1.0" rapbqvat="ebg13"?>
an XML parser will recognize that the document is stored in the traditional ROT13 encoding.

(( Joe English, http://www.flightlab.com/~joe/sgml/faq-not.txt ))

Re: [9fans] debugging rc

[erik quanstrom]

> On Tuesday 05 of July 2011 09:31:43 Rudolf Sykora wrote:
> > (...)
> > Is there any better way? Can rc be told to give some
> > more helpful info?
>
> there are:
> flag x +
> flag r +
>
> the output produced by r + is somewhat strange, but may be good enough. In your case, it shows difference between *$a* and *$a^*:
>
> the former is:
>
> Xdol (a*) () ()
> Xmark () ()
> Xword () () ()
> Xconc (*) () ()
> rc: null list in concatenation

this is a trace of the rc virtual machine.  it's not easy to follow, or
helpful in most cases.

if the problem is the null list in concatination, i made a small change
to rc to give more information about these problems in the error
message on steve's suggestion.

this version of rc is available as quanstro/futharc or on the 9atom
cd.

- erik