Hi guys, I've been given a command line program that is an executable (.exe) that I was asked to automate on Win32. The task was simple; First enter a number, Enter a string, than 'Press any key to continue...' (dos system call it seems). And the program will reply successful if those values were valid. I decided to use IPC::Open2. The code was as follows.. 
use strict;
use warnings;
use IPC::Open2; 

my $cmd = 'C:\temp\abc.exe'; 
my $pid = open2(*RR,*WW,$cmd); 

print WW "5 \n";
print WW "iAmString \n";
print WW "\n"; # any key

while (<RR>) {
   chomp($_); 
   print "$_\n";
}
print "done \n";

[download]
But the code did not work at all - it froze on the <RR> block. So I went ahead a compiled a simple C code to simulate the problem. 
int main(int argc, char** argv) {
    printf ("Hello World \n");

    int value1;
    printf ("I am a number: ");
    scanf("%d", &value1);
    printf ("This is your number: %d \n",value1);

    char ppp[20];
    printf ("I am a string: " );
    scanf("%s",&ppp);
    printf ("This is your string? %10.10s \n",ppp);

 // system("PAUSE");
    return (EXIT_SUCCESS);
}

[download]
And, the perl script was stuck at the blocking <RR> as expected. I changed the C Program and removed the 'system("pause") - press any key to continue' command, and it worked brilliantly. It appears to me that after the main part of the C program is executed it is blocked by 'cmd.exe /c PAUSE' that I believe is spawned as a blocking child process. i.e i can't write "<any key>" to the process I created through open2. Rather I might have to send <any key> to the cmd.exe that was spawned as a child of abc.exe. Is there a workaround for this? (I don't have access to the source code of the executable, so i can't simply remove the system("PAUSE"). Help is a appreciated.

In reply to Perl Open2/3 and .exe by markusk

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