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hello,

i am calling an external command in perl on win32 as follows

my $app = 'c:\program files\foo\flarp.exe status quux';
my $spam = qx/ $app 2>&1 /;

now i need to get the status of executed command

if ( $? == 0 ) { print "yay"; }

the problem is it always returns 0. since quux is not running, when i
run the same command on cmd.exe i get return value as 3

> echo %ERRORLEVEL%
3

i have checked the archives with similar question but no help. i have
also checked system() and qx// documentation but they don't have
anything like this.

is there any other way to do this?

thanks.

On Wed, 15 Jul 2009 17:16:54 +0100, Ben Morrow <> wrote:

>
>Quoth alfonsobaldaserra <>:
>>
>> i am calling an external command in perl on win32 as follows
>>
>> my $app = 'c:\program files\foo\flarp.exe status quux';
>> my $spam = qx/ $app 2>&1 /;
> ^^^^
>This means that the command will be run through cmd.exe, which exits
>successfully (despite the command having failed).
>
>> now i need to get the status of executed command
>>
>> if ( $? == 0 ) { print "yay"; }
>
>$? contains the exit value of the cmd.exe process (since that's the only
>thing cmd.exe knows about). Apparently this is always 0.
>
>I would recommend using Win32:rocess instead. It's a little awkward,
>but should let you do the redirection without involving cmd. You will
>have to create the pipe and read from it by hand, of course.
>
>Ben

Why wouldn't system work?

Docs:

if ($? == -1) {
print "failed to execute: $!\n";
}
elsif ($? & 127) {
printf "child died with signal %d, %s coredump\n",
($? & 127), ($? & 12 ? 'with' : 'without';
}
else {
-->>> printf "child exited with value %d\n", $? >> 8;
}

Or does Perl/system spawn processes on everything except Windowz?

-sln

>
> Why wouldn't system work?
>
> * *if ($? == -1) {
> * * * * print "failed to execute: $!\n";
> * * }

thank you for response. i tried with system and $? but it still
returns 0. however it should return 3.

any more ideas?

thanks.

On 16 jul, 13:30, alfonsobaldaserra <alfonso.baldase...@gmail.com>
wrote:
[...]
>
> any more ideas?

I would recommend module IPC::Run3, which does a very portable and
Perlish way to do the redirects:

use strict;
use IPC::Run3;
my ($stdout, $stderr);
my @app = ('c:/program files/foo/flarp.exe', 'status',  'quux');
run3(\@app, \undef, \$stdout, \$stderr);
if ( $? == 0 ) { print "yay"; }

Note that the external application and its command-line parameters are
in an array, avoiding the detour via cmd.exe and that stdout and
stderr can be captured separately. The \undef connects stdin to /dev/
null (or the Win32 equivalent NUL). Also, pathnames in Win32 Perl may
be written with forward slashes.

>

> use strict;
> use IPC::Run3;
> my ($stdout, $stderr);
> my @app = ('c:/program files/foo/flarp.exe', 'status', *'quux');
> run3(\@app, \undef, \$stdout, \$stderr);
> if ( $? == 0 ) { print "yay"; }
> 

i tried running this code. for some obscure reasons it was showing
unexpected results when using command as array, it wasn't executing
the program in background at all, so i did
my $app = q[ c:/program files/foo/flarp.exe status quux ];
and it started executing but there came another problem. the return
value ($?) was always 0 now. i tried the same code with other
commands and it was working just not for this particular program.

before i give up i want to thank you for making me aware of
IPC::Run3. plus i learnt that there exists a File::Spec->devnull() to
redirect $stdout and $stderr messages to.

many thanks.