shell redirect on windows, qx?

doom has asked for the wisdom of the Perl Monks concerning the following question:

I understand there are several different flavors of perl on Windows boxes (vanilla, strawberry, active state, cygwin...), and I was wondering whether they come with anything like a Bourne shell, in particular, I was wondering how they handle redirection when shelling out with qx{} (aka backticks).

If you windows users do something like this, would you expect it to work (i.e. to give you the standard output mixed with any error messages)?

my $captured_output = qx{ some_command 2>&1 };

In fact, if you're a windows/perl person, do you think you could run the following code and report back what kind of output you see?

use File::Temp qw( tempfile );
use File::Spec qw( devnull );
$|=1;

my $code =<<'CODE';
  $|=1;
  print "ABC\n";
  print STDERR "012\n";
  print "IJK\n";
  print STDERR "345\n";
  print "XYZ\n";
  print STDERR "678\n";
CODE

# create a temporary perl script file
my ($fh1, $scriptname) = tempfile( 'yap_XXXX', SUFFIX => '.pl');
print {$fh1} $code;
close( $fh1 );

my $perl = $^X;
my $devnull = File::Spec->devnull;
print "No redirect: \n";
print qx{ $perl $scriptname }, "\n";
print "Redirect errors to devnull: \n";
print qx{ $perl $scriptname 2>$devnull }, "\n";
print "Redirect merging stderr and stdout: \n";
print qx{ $perl $scriptname 2>&1 }, "\n";
[download]

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Re: shell redirect on windows, qx? by BrowserUk (Patriarch) on Apr 11, 2008 at 21:01 UTC
This is perl 5.8.6/AS811 on XP: c:\test>perl use File::Temp qw( tempfile ); use File::Spec qw( devnull ); $\|=1; my $code =<<'CODE'; $\|=1; print "ABC\n"; print STDERR "012\n"; print "IJK\n"; print STDERR "345\n"; print "XYZ\n"; print STDERR "678\n"; CODE # create a temporary perl script file my ($fh1, $scriptname) = tempfile( 'yap_XXXX', SUFFIX => '.pl'); print {$fh1} $code; close( $fh1 ); my $perl = $^X; my $devnull = File::Spec->devnull; print "No redirect: \n"; print qx{ $perl $scriptname }, "\n"; print "Redirect errors to devnull: \n"; print qx{ $perl $scriptname 2>$devnull }, "\n"; print "Redirect merging stderr and stdout: \n"; print qx{ $perl $scriptname 2>&1 }, "\n"; ^Z No redirect: 012 345 678 ABC IJK XYZ Redirect errors to devnull: ABC IJK XYZ Redirect merging stderr and stdout: ABC 012 IJK 345 XYZ 678 [download] Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply] [d/l]
Re^2: shell redirect on windows, qx? by doom (Deacon) on Apr 11, 2008 at 21:17 UTC
Ah, cool. It looks like Active State perl behaves very much like a unix-box in this respect. Thanks for the reply.	[reply]
Re^3: shell redirect on windows, qx? by BrowserUk (Patriarch) on Apr 11, 2008 at 21:28 UTC
It looks like Active State perl behaves ... It's not down to AS perl. The redirection is done by the shell processor that is invoked by qx/backticks or system. Under AS perl that shell is the standard win32 cmd.exe. Other variants, such as cygwin builds and Strawberry etc. may choose to invoke a different shell. I think cygwin (as standard) uses a `sh`-alike, but you can probably get `csh`, `bash` or `zsh` that would run under cygwin. (If you must:), but you might have to configure something somewhere to get them used by default, and each has its own set of advantages and restrictions as with the *nix brethren. In theory, there is nothing to stop you from configuring a cygwin build to use cmd.exe, but I've no idea how. Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply] [d/l] [select]
Re: shell redirect on windows, qx? by mr_mischief (Monsignor) on Apr 11, 2008 at 21:53 UTC
The only one that comes with a bash is the Cygwin environment. Fortunately, the Windows CLI is mostly sane for redirection purposes, though. Unfortunately, I found that older versions of ActiveState might break on your code. Anything recent should be okay, though. To keep the response a bit shorter for those looking for just the gist, I'll put all but my newest copy of each in a readmore. I don't have Vanilla, but it's my understanding Vanilla is just a proper subset of Strawberry. I'd mostly expect similar results from those two. Strawberry 5.8.8: Read more... (345 Bytes) Strawberry Perl 5.10.0.1: `No redirect: 012 345 678 ABC IJK XYZ Redirect errors to devnull: ABC IJK XYZ Redirect merging stderr and stdout: ABC 012 IJK 345 XYZ 678` [download] ActiveState 5.8.0 (build 804): Read more... (503 Bytes) ActiveState 5.8.8 (build 822): Read more... (345 Bytes) ActiveState 5.10.0 (build 1002): `No redirect: 012 345 678 ABC IJK XYZ Redirect errors to devnull: ABC IJK XYZ Redirect merging stderr and stdout: ABC 012 IJK 345 XYZ 678` [download] Cygwin Perl 5.8.6: `No redirect: 012 345 678 ABC IJK XYZ Redirect errors to devnull: ABC IJK XYZ Redirect merging stderr and stdout: ABC 012 IJK 345 XYZ 678` [download]	[reply] [d/l] [select]