[Perl-beginners] Write stdout to a file as well as stdout

perldoc -f open

One solution would be to use a custom subroutine instead of print()ing
directly. If you need something more robust, there are modules out
there that can do the heavy lifting for you.


#####################

use strict;
use warnings;
open(OUTFILE,">script.log") || die "Couldn't write to script.log!\n";

PrintOut("This goes to a file as well as the screen.\n");

sub PrintOut{
print @_;
print OUTFILE @_;
}

#####################





-----Original Message-----
From: Larry Guest
Sent: Tuesday, January 11, 2005 3:40 PM
To: 'Perl Beginners Mailing List'
Subject: Write stdout to a file as well as stdout

I have a script that does all kinds stuff.
When its running it outputs all kinds of useful information to the
screen and exits.

What I want to do is have this also sent to a file.

[Tim Johnson] <snip>

- or die is better than || die
- why go to all the trouble of giving an error if you don't use the
error? (IE $!) :)
Why use a subroutine just to print to a filehandle?

Also you didn't ever close it which could be bad :)

use strict;
use warning;
open FH, '>./script.log' or die "Open script.log for writing failed: $!";
print LOG "print to LOG like whenever you want to add something to it\n";
close FH;

You may also want to consider locking it either with flock if your
system supports it or creating/deleting/checking for a lock file.

why not just re-direct from the command line if all output is needed?

perl.program > output.file

You want to replicate the `tee` command. From its manpage:

NAME
tee - pipe fitting

SYNOPSIS
tee [-ai] [file ...]

DESCRIPTION
The tee utility copies standard input to standard output, making
a copy in zero or more files. The output is unbuffered.

The following options are available:

-a Append the output to the files rather than overwriting them.

-i Ignore the SIGINT signal.

The following operands are available:

file A pathname of an output file.

The _Perl Cookbook_ has recipies showing how to replicate this
behavior, e.g.:

open(MANY, "| tee file1 file2 file3 > /dev/null") or die $!;
print MANY "data\n" or die $!;
close(MANY) or die $!;

Or, to make the print statements simpler,

# make STDOUT go to three files, plus original STDOUT
open (STDOUT, "| tee file1 file2 file3") or die "Teeing off: $!\n";
print "whatever\n" or die "Writing: $!\n";
close(STDOUT) or die "Closing: $!\n";

Or look on CPAN for modules like Tie::Tee and IO::Tee.

Larry Guest [LG], on Tuesday, January 11, 2005 at 15:40 (-0800)
contributed this to our collective wisdom:

LG> I have a script that does all kinds stuff.
LG> When its running it outputs all kinds of useful information to the
LG> screen and exits.
LG> What I want to do is have this also sent to a file.
LG> Any thoughts?

We have module for that, and here is also small example:

use IO::Tee;

my $tee = new IO::Tee(\*STDOUT, ">log.txt");
print join(' ', $tee->handles), "\n"; #could go away
for (1..10) { print $tee $_, "\n" } #print to $tee handles
$tee->flush;
__END__

helps ?