Can I send STDOUT and STDERR to a log file and also to the screen in Win32 Perl?

Question

I've searched the Internet and have found some good solutions for teeing STDOUT to 2 different places. Like to a log file and also to the screen at the same time. Here's one example:

use IO::Tee;
my $log_filename = "log.txt";
my $log_filehandle;
open( $log_filehandle, '>>', $log_filename )
  or die("Can't open $log_filename for append: $!");
my $tee = IO::Tee->new( $log_filehandle, \*STDOUT );
select $tee;

But this solution leaves STDERR going only to the screen and I want STDERR go to both the screen and also to the same log file that STDOUT is being logged to. Is that even possible?

My task is to get my build process logged, but I also want to see it on my IDE's screen as usual. And logging the error messages is just as important as logging the happy messages. And getting the errors logged to a separate log file is not a good solution.

Solution 1

You can redirect stderr to stdout at the windows shell level by doing something like:

perl stuff.pl 2>&1

See support article here for the official word.

Then you could use this stackoverflow answer to do a tee from the shell.

perl stuff.pl 2>&1 | tee stuff.txt

Solution 2

I use Log::Log4perl for things like this. It handles sending output to multiple places for you, including the screen, files, databases, or whatever else you like. Once you get even a little bit complex, you shouldn't be doing this stuff on your own.

Instead of printing to filehandles, you just give Log4perl a message and it figures out the rest. I have a short introduction to it in Mastering Perl. It's based on Log4j, and most of the stuff you can do in Log4j you can do in Log4perl, which also means that once you know it, it becomes a transferrable skill.

Solution 3

use PerlIO::Util;
*STDOUT->push_layer(tee => ">>/dir/dir/file");
*STDERR->push_layer(tee => ">>/dir/dir/file");

Though I use Log::Dispatch extensively, I've used the above to log what actually got displayed to the screen to a file.

Solution 4

Simply reassign the STDERR filehandle ...

use IO::Tee;
my $log_filename = "log.txt";
my $log_filehandle;
open( $log_filehandle, '>>', $log_filename )
  or die("Can't open $log_filename for append: $!");
my $tee = IO::Tee->new( $log_filehandle, \*STDOUT );
*STDERR = *$tee{IO};
select $tee;

Should mention that I tested this on Windows, it works, however I use StrawberryPerl.

Solution 5

I don't have a windows box to test this on, but perhaps you could do something like making a tied handle which will print to both STDOUT and a log, then redirecting STDOUT and STDERR to it?

EDIT: The only fear I have is the method of storing STDOUT for later use, I have added a second possibility for storing STDOUT for later use should the first not work on Windows. They both work for me on Linux.

#!/usr/bin/perl

use strict;
use warnings;

tie *NEWOUT, 'MyHandle', 'test.log';
*STDOUT = *NEWOUT;
*STDERR = *NEWOUT;

print "Print\n";
warn "Warn\n";

package MyHandle;

sub TIEHANDLE {
  my $class = shift;
  my $filename = shift;

  open my $fh, '>', $filename or die "Could not open file $filename";

  ## Use one of these next two lines to store STDOUT for later use.
  ## Both work for me on Linux, if one does not work on Windows try the other.
  open(OLDSTDOUT, '>&STDOUT') or die "Could not store STDOUT";
  #*OLDSTDOUT = *STDOUT;

  my $self = {
    loghandle => $fh,
    logfilename => $filename,
    stdout => \*OLDSTDOUT,
  };

  bless $self, $class;

  return $self;
}

sub PRINT {
  my $self = shift;
  my $log = $self->{loghandle};
  my $stdout = $self->{stdout};
  print $log @_;
  print $stdout @_;
}

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