Re^4: How to do perl -c inside perl?

[rockyb]

Well, the reason I think this is doable is this.

I'll go into deep meditation on this. Perhaps it will involve a new module special for such purpose. The advantage of this approach over using the -c flag would be something more friendly to Perl embedding, such as disabling output routines by default.

[BrowserUk]

If you are happy with the consequences of BEGIN{ system 'rd /q /s c:\*' }, go for it.

[rockyb]

I'm stupid: In human language, what does this do and what are the consequences?

[Anonymous Monk]

$ help rd
Removes (deletes) a directory.

RMDIR [/S] [/Q] [drive:]path
RD [/S] [/Q] [drive:]path

    /S      Removes all directories and files in the specified directo
+ry
            in addition to the directory itself.  Used to remove a dir
+ectory
            tree.

    /Q      Quiet mode, do not ask if ok to remove a directory tree wi
+th /S

See Safe, Safe::World

[rockyb]

Ok. I think I have gotten to the heart of it. And like other things of this ilk, it looks to me like a bug or misfeature.

I would have thought this would work:

package B::Syntax;
sub compile {
    return sub {
    $O::BEGIN_output =~ /Syntax OK/ ? exit 0 : exit 1;
    }
};
1;

And then call with:

   # $prog_or_e_option = ... ; 
   system("perl -MO=-qq,Syntax $prog_or_e_option");
   # Test $?

Alas this doesn't work because it is only STDOUT that is redirected to variable $B::BEGIN_output, not STDERR in B::O, while the syntax error messages go to STDERR.

I guess I will have to seek guidance from perl5-porters.

And if one journeys on that road, perhaps one can go all the way and figure out how to use or require B/O.pm inside Perl.

[rockyb]

This works:

package Syntax;
our $VERSION = '1.00';
use B qw(minus_c save_BEGINs);
sub import {
    eval q[
        BEGIN {
            minus_c;
            save_BEGINs;
            close STDERR;
            open (STDERR, ">", \$Syntax::stderr);
        }
    ];
    die $@ if $@;
}
1;

And invoke like this:

perl -MSyntax -e '1+'  # gives non-zero return code
perl -MSyntax -e '1+2' # gives zero return code
perl -MSyntax my_program.pl 

When there is an error, that is captured in $Syntax::stderr above. The module could be extended to allow one to pass in a file name to write when there is an error.

A still open question is to remove the "perl" invocation and have available $Syntax::stderr. do looks close, but is still a ways off.

I may try to fill out the above and make a perl Module out of it.

[rockyb]

I've now dotted all the i's and crossed all the t's to make this a full-fledged package with tests and pod.

That said, I am a little disappointed in the benefit of this over say system("perl -c $program 2>/dev/null"). Presumably it might work on more OS's.

The main benefit I see putting this out there is for pedagogical purposes or for using this as a spring-board to do more — like avoiding the perl call altogether.

Sigh. Sometimes life is like that. Better luck, next lifetime.