Two part question:

I'm using IPC::Open3 on Win32 to avoid the shell. Notice how double quotes are handled below. I'm assuming this is a Windows issue and not a Perl issue, correct? Extra points if you can explain the logic of this. ;)

#!/usr/bin/perl -w
use strict;

use IPC::Open2;

my @command = (
      'perl',
      'my test.pl',
      'first arg1',
      '"second arg2"',
      'word "quoted" and \"backslashed\" word',
      '"2word "quoted" and \"backslashed\" word"',
);

my $pid = IPC::Open2::open2( \*r, \*w, @command );

print "Pid = $pid\n";
print "output:\n";
print while $_ = <r>;
print "done\n";
[download]

With output on Win32 as:

Pid = 316925
output:
316925 [first arg1]
316925 [second arg2]
316925 [word]
316925 [quoted]
316925 [and]
316925 ["backslashed"]
316925 [word]
316925 [2word quoted and "backslashed" word]
316925 done
done
[download]

Part two of my IPC::Open3 question:

The docs say to call waitpid($pid,0) to reap the child process -- and indeed the windows process table fills up (64 processes?) if waitpid isn't called.

See, I've got a function that returns a file handle. Under Windows it uses IPC::Open3, otherwise it does a open($fh,'-|') call. So the code that calls this function isn't suppose to know or care about how that file handle is generated.

The question is about when to call waitpid() on Windows. I assume it must be called after calling close() (or after the returned file handle goes out of scope). Is that a correct assumption?

If waitpid() has to be called after the close() that means the function that returns the file handle must store the PID some place. So, seems like I need to tie the handle.

Here's my code. I have a few follow-up questions at the end:

#!/usr/bin/perl -w
use strict;

my %self;

my @command = (
    'perl', 
    'my test.pl', 
    'one arg',
    '"two arg"'
);

{
my $fh = windows_fork( \%self, @command );
print while <$fh>;
}
print "out of scope\n";
exit;

sub windows_fork {
    my ( $self, @args ) = @_;
    require IPC::Open2;
    my ( $rdrfh, $wtrfh );
    # Deal with windows quotes
    my @command = map { s/"/\\"/g; qq["$_"] }  @args;
    my $pid = IPC::Open2::open2($rdrfh, $wtrfh, @command );
    binmode $rdrfh, ':crlf';

    tie *handle, 'call_waitpid', $rdrfh, $pid;
    return \*handle
}
package call_waitpid;
use strict;

sub TIEHANDLE {
    my ( $class, $fh, $pid ) = @_;
    bless {
        handle  => $fh,
        pid     => $pid,
    }, $class;
}

sub READLINE {
    my ( $self ) = @_;
    my $fh = $self->{handle};
    return <$fh>;
}


sub DESTROY {
    my ( $self ) = @_;
    close $self->{handle};
    waitpid $self->{pid}, 0;
}
[download]

Questions:

1. Is this how you would deal with this issue. Use a tied handle to track the PID?
2. In READLINE I cannot do: return <$self->{handle}>; why?

     syntax error at fork.pl line 81, near "<$self->{handle"
   [download]

3. In the "windows_fork() sub I'm blessing a typeglob. The problem is it's the same typeglob for every call to windows_fork(). So if windows_fork() is called twice the handles are mixed. I tried using gensym() but couldn't get that to work. I need a way to have more than one file handle active at a time.

my $fh = windows_fork( \%self, 'perl', 'my test.pl', 'first stuff');
my $fg = windows_fork( \%self, 'perl', 'my test.pl', 'other stuff');
print while <$fh>;
[download]

Results in "other stuff" from $fh.

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