Re: Human readable flatfiles

[Philip Mak]

On Wed, 31 May 2000, Perrin Harkins wrote:

Thanks for the reply. I have a few problems though:

 You need to read up a little on modules and "require" in Perl5.
 
 The quick and dirty solution is to use "do" instead of require.  That will
 solve your immediate problem, but you'll still be reading the files every
 time which might eventually become a performance hit.

I can't seem to get "do" to work. I did this:

my $series_name;
do "series_$series.i"; # -- note include filename depends on a variable
print "$series_name\n";

but $series_name comes out undefined, even though series_$series.i (in
this case, series_ranma.i) sets $series_name.

I also tried the package thing:

 What I do when I have things like config files is make actual unique
 packages of them.  For example:
 
 (In My/Module.pm)
 package My::Module;
 # don't use strict here
 $foo = 7;
 
 (In some other program)
 use My::Module;
 print "$My::Module::foo\n";

How would this work if the include filename has to depend on a variable? I
think I have the parsing wrong; I kept getting error messages. e.g.
something like:

use $series;
print "$$series::series_name\n";

 Honestly though, your example makes it look like you'd be better off with
 dbm files and Tie::MLDBM or something.

The database files would have to be human readable though, such that they
can be edited by a text editor. The data that I am making includes an
index to content that is maintained by other webmasters. The other
webmasters don't even know how to use a UNIX shell, so I have to keep it
simple for them. If I used a binary file format I'd have to make them
learn the tools for changing it.

-Philip Mak ([EMAIL PROTECTED])

Re: Human readable flatfiles

[Perrin Harkins]

Philip Mak wrote:
 I can't seem to get "do" to work. I did this:
 
 my $series_name;
 do "series_$series.i"; # -- note include filename depends on a variable
 print "$series_name\n";

Your lexical ("my") variable in the same scope is taking precedence, and
the "do' is not allowed to see lexicals in its enclosing scope.  If you
make $series_name a global, I think it will work.  The alternative is to
read the file yourself and eval it, which would allow it to see the
lexical.

 I also tried the package thing:
 
  What I do when I have things like config files is make actual unique
  packages of them.  For example:
 
  (In My/Module.pm)
  package My::Module;
  # don't use strict here
  $foo = 7;
 
  (In some other program)
  use My::Module;
  print "$My::Module::foo\n";
 
 How would this work if the include filename has to depend on a variable? I
 think I have the parsing wrong; I kept getting error messages. e.g.
 something like:
 
 use $series;
 print "$$series::series_name\n";

If it depends on a variable, replace the "use" with "require".  The
"use" statment is evaluated at compile time, and "require" at run time.

Keep in mind that require only loads each file once, so if you need to
show changes in these files that happen while the server is running this
won't work for you.

  Honestly though, your example makes it look like you'd be better off with
  dbm files and Tie::MLDBM or something.
 
 The database files would have to be human readable though, such that they
 can be edited by a text editor. The data that I am making includes an
 index to content that is maintained by other webmasters. The other
 webmasters don't even know how to use a UNIX shell, so I have to keep it
 simple for them. If I used a binary file format I'd have to make them
 learn the tools for changing it.

Depending on how much of this data you have and how timely it has to be,
you could make a cron that crawls the text files every 5 minutes or so
and build a dbm with their data in it.

- Perrin

Human readable flatfiles

[Philip Mak]

Hello,

I would like to ask a question about maintaining human readable flatfiles
in general.

I have a perl (non-modperl) program that needs some input data. Currently,
it reads in the data by "require"ing another perl script that has
statements to set the variables (as global variables). I did it this way
so that I can easily edit the include file if I want to change values,
and I can even put code in the include file to calculate values.

But, I am finding that this does not work in modperl under "use strict".
Apparently, code in a file called by require is not in the same variable
scope. (If "use strict" is off, it works sometimes but other times the
variables come out with the values from the previous invocation.)

Here is an example of what I currently have:

$series = $ENV{'QUERY_STRING'};
require "series_$series.i";
(do something with the variables $series_name, $series_prefix)

and inside series_ranma.i, I have:

$series_name = 'Ranma 1/2';
$series_prefix = 'Ranma';
@series_data = (
insert list here
);

but this does not work, since in modperl the required file has a different
variable scope.

Two ideas I am thinking of are:

(1) make series_$series.i into a text file instead, like this:

Ranma 1/2
Ranma
insert list here

and read it in with fopen(SERIES, "series_$series.i") and SERIES. But
then I wouldn't be able to put perl code inside it and it is less clear.

(2) make series_$series.i into a subroutine that returns its values. I can
require it, and then call the subroutine and get the return values, but
this seems kind of kludgy to me.

Does anyone have a better suggestion for maintaining human readable
flatfiles containing data to be read? Is there a good CPAN module for it
perhaps?

Thanks,

-Philip Mak ([EMAIL PROTECTED])

P.S. When replying to this message, please make sure my e-mail address is
in the to field. I'm not sure if I'm subscribed to this mailing list or
not. It seems to keep kicking me off or something, because I haven't been
receiving any mail from it.

Re: Human readable flatfiles

[Perrin Harkins]

 I have a perl (non-modperl) program that needs some input data. Currently,
 it reads in the data by "require"ing another perl script that has
 statements to set the variables (as global variables). I did it this way
 so that I can easily edit the include file if I want to change values,
 and I can even put code in the include file to calculate values.

 But, I am finding that this does not work in modperl under "use strict".
 Apparently, code in a file called by require is not in the same variable
 scope. (If "use strict" is off, it works sometimes but other times the
 variables come out with the values from the previous invocation.)

You need to read up a little on modules and "require" in Perl5.

The quick and dirty solution is to use "do" instead of require.  That will
solve your immediate problem, but you'll still be reading the files every
time which might eventually become a performance hit.

What I do when I have things like config files is make actual unique
packages of them.  For example:

(In My/Module.pm)
package My::Module;
# don't use strict here
$foo = 7;

(In some other program)
use My::Module;
print "$My::Module::foo\n";

Honestly though, your example makes it look like you'd be better off with
dbm files and Tie::MLDBM or something.

- Perrin