Hi All, I am a long term on-and-off programmer but new to Perl. I pinched this spawn_server/spawn_client example off the net because I need to pass a process that is waiting for more input back from a module. This example seemed to provide the pieces I need. As it stands, it works on my (Windows) box. All I had to do to make it work was change the process call paths. But when I make the substitutions in the "Changed" sections to use IO::File - so that I can pass the process' STDIN around between subs - it doesn't work. Obviously I am misunderstanding the relationship between normal handles and IO::File. Can anyone point me in the right direction? I have read (several times) tutorials on the net about passing references but only including the entries in the name table that are file handles - I tried, but that had me lost. IO::File looked a lot simpler :-) 

use Win32::Process;
# First file spawn_server.pl

#===================== V Added   1    V ==============================
use IO::File ;
my $savein = new IO::File ;
#===================== A Added   1    A ==============================

%Data = ( one =>1, two =>2, three =>3 );


pipe(READ, WRITE);
select(WRITE);
$| = 1;
select(STDOUT);

#=====================  V  Changed 1  V ==============================
+=
#$savein->open ( "< &STDIN" ) ||  die "Can not save STDIN\n";
open(SAVEIN, "< &STDIN")  ||  die "Can not save STDIN\n";
#=====================  A  Changed 1  A ==============================
+=

open(STDIN, "< &READ")    ||  die "Can not redirect STDIN\n";
select(STDIN);
$| = 1;
select(STDOUT);

Win32::Process::Create 
  ( $Proces , "c:\\perl\\bin\\perl.exe", "c:\\perl\\bin\\perl.exe c:\\
+db2maint\\cmd\\perl\\spawn_client.pl",
    1       , NORMAL_PRIORITY_CLASS    , "c:\\db2maint\\test" 
  );

#=====================  V  Changed  2 V ==============================
+=
#open(STDIN, "< &savein");
open(STDIN, "< &SAVEIN");
#$savein->close () ;
close(SAVEIN);
#=====================  A  Changed  2 A ==============================
+=

close(READ);
print "$0: Sending variables to child...\n";
foreach $Temp (keys(%Data)){
    print "$0:\t$Temp=$Data{$Temp}\n";
    print WRITE "\$Data{$Temp}=$Data{$Temp};\n";
}
print "$0: Finished sending variables.\n";
close(WRITE);
print "$0: About to terminate. Waiting for <RETURN> to be hit...\n";
<STDIN>;
print "$0: End.\n";

[download]
# Separate file - spawn client.

print "$0: Starting.\n";
print "$0: Reading in variables...\n";
while(<STDIN>){
    eval($_);
    print "$0: \t$_";
}
print "$0: Finished reading variables.\n";
print "$0: Dumping variables...\n";
foreach $Temp (keys(%Data)){
    print "$0:\t$Temp=$Data{$Temp}\n";
}
print "$0: End.\n";

[download]

Note, both files do run with the substitutions in place but nothing seems to get passed to the client.

In reply to How do you redirect STDIN using IO::File ? by malJam

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