The problem on Win32, is that Win32 dosn't support "select" on pipes. IPC::Open3 uses pipes to connect to the command, while IPC::Run uses sockets( win32 select works on sockets). BUT, if you can figure out a way to NOT use select, and get the pipes flushed, you may be able to use it. Your main problem is output may be sitting in the pipe,
but without $select->can_read, you won't know it. See Pipe Problem for some ideas. I don't use MSwindows, but there probably are hacks to get around the problem, like
using sysread to read 1 byte at a time, until nothing is there, or see Non-blocking Reads from Pipe Filehandle You can use the SuperSearch here for many examples of using Open3, but remember, no select is available to you... so you need a workaround. See Perl/Tk App and Interprocess Communication. If you are using an event-loop system, you can setup a timer to repeatedly read the pipe until no bytes are there. Also see " perldoc -q 'capture STDERR' "
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How difficult do you think it would be to try and work with IPC::OPen3, especially since I'm a beginner? I really need to get this done this week and its seeming impossible for me to do since I don't have alot of Perl experience.
Thanks for any help,
J
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Using IPC::Open3, in it's simplest form, is very easy; BUT your windows command may be problem-prone.. all you can do is give it a quick try. Here is a very simple usage for doing a fast go/no-go test. See if you can print to your command, then collect all output. Uncomment the while(1){} code block, if you want to loop. Also note the sysread method, in case your <> read hangs. So give this a try, and report back your code and any problems you encounter.
#!/usr/bin/perl
use warnings;
use strict;
use IPC::Open3;
my $pid = open3(\*WRITE, \*READ, \*ERROR,"your_command");
if( ! $pid ){ die "$!\n";}
#my $pid = open3(\*WRITE, \*READ,0,"your_command");
#if \*ERROR is false, STDERR is sent to STDOUT
#while(1){
print "Enter a string to evaluate\n";
chomp(my $query = <STDIN>);
#send query to command
print WRITE "$query\n";
#give small time to output
select(undef,undef,undef,.5); #half second delay
#get the answer from command
chomp(my $answer = <READ>);
print "$query = $answer\n";
# you may need something with sysread, if <READ> hangs
# my $bytes_read = sysread(READ, my $buf, 1024);
# print "$query = $buf\n";
#get the error from command
chomp(my $error = <ERROR>);
print "$query error = $error\n";
#}
waitpid($pid, 1);
# It is important to waitpid on your child process,
# otherwise zombies could be created.
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Thanks I'll have a look at them. I suspect being a novice isn't gonna help me much :)
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I am also having the same problem. Any solution found, pleae share the same. | [reply] |