See select , open , close

Especially the docs for open have explicit sample code for exactly this task.

°) called "duplicate"

In particular, from open:

Here is a script that saves, redirects, and restores STDOUT and STDERR using various methods:

    #!/usr/bin/perl
    open(my $oldout, ">&STDOUT") or die "Can't dup STDOUT: $!";
    open(OLDERR, ">&", \*STDERR) or die "Can't dup STDERR: $!";
    open(STDOUT, '>', "foo.out") or die "Can't redirect STDOUT: $!";
    open(STDERR, ">&STDOUT") or die "Can't dup STDOUT: $!";
    select STDERR; $| = 1; # make unbuffered
    select STDOUT; $| = 1; # make unbuffered
    print STDOUT "stdout 1\n"; # this works for
    print STDERR "stderr 1\n"; # subprocesses too
    open(STDOUT, ">&", $oldout) or die "Can't dup \$oldout: $!";
    open(STDERR, ">&OLDERR") or die "Can't dup OLDERR: $!";
    print STDOUT "stdout 2\n";
    print STDERR "stderr 2\n";
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#11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.

Ok, thanks for the replies.

Rolf, are you saying that the OP’s strategy would work?   I presume that you are referring to the paragraph in perldoc -f open which begins “Here is a script that saves, redirects, and restores "STDOUT" and "STDERR" using various methods:” but I do get pretty-lost pretty-fast when reading it.   Could you perhaps offer a couple of specific examples that do, specifically, what the OP has in mind to do?   Or, otherwise, elaborate on how you’d do it?

There are plenty of specific and working examples in this thread!

The confusion stems from demonstrating more than one way to do it within the same sample script (like 3 vs 2 argument open AND lexical filehandles vs bare words AND addressing filehandles as globrefs)

I have to admit that Perldocs are overly confusing in this respect.

Cheers Rolf

_{(addicted to the Perl Programming Language and ☆☆☆☆ :)}

Some example code snippets that work...

    # preserve STDOUT
    open $oldSTDOUT, ">&STDOUT" || warn "Can't preserve STDOUT\n$!\n";
+ 
    close STDOUT;
 
    # preserve STDERR 
    open (OLDER, ">&", \*STDERR) || warn "Can't preserve STDERR\n$!\n"
+;
    close STDERR;

    # if you want to capture any messages in the meantime, point STDER
+R to a memory location
    open (STDERR, ">", \$err) || warn "Can't redirect STDERR\n$!\n";

    # restore STDERR 
    open (STDERR, ">&", \*OLDER) || warn "Can't restore STDERR\n$!\n";
    close OLDER;

    # restore STDOUT
    open STDOUT, ">&", $oldSTDOUT;

    # you may want to flush buffers at some point
    select STDERR; $| = 1;
    select STDOUT; $| = 1;
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