Print output of subroutines captured in backticks?

[Mr. Nice Guy]

Hi,

In ksh, I can do something like this:

blat()
{
print "blat says foo"
return 0
}
junk=`blat`
rv=$?

In which case, "$junk" holds "blat says foo", while "$rv" holds 0, or
whatever blat() actually returns. This is really useful in capturing
an error message from the function, as well as the actual return code.

How would I do this in Perl, where I capture the print() statements of
the sub in a variable, but the return value separately? Something
along the lines of:

sub blat ()
{
print "blat says foo";
return 0;
}

my( $junk, $rv );

$junk = `blat`; # -- this doesn't actually work, since blat() isn't
an external executable
$rv = $?;

What I want is whatever blat() might have output via print()
statements into $junk rather than STDOUT, but the return value of the
function in a separate variable; $rv in this case.

I know I can use something like:

sub blat ()
{
print "This will be sent to STDOUT\n";
die( "This will get caught by the eval{ ... }" );
}

eval { blat() };
print $@ if $@;

But this is different.

A. i'm limited to whatever I provide in die(), rather than any or all
output from the function. Don't get me wrong: "eval { ... }" is
useful, and I do use this.

B. die()'s return value is going to be 1 in most, if not all, cases,
not whatever I want to return. Unless there's a way to return a
different value; setting $! didn't seem to work.

[Andrzej Adam Filip]

Use "select" to redirect output of "print without specific file-handle"
to string (IO::String);

use IO::String;
my ($returnCode, $output);
my $io = IO::String->new($output);
my $oldfh = select($io);
eval { $returnCode = &blat() };
select($oldfh);

print "returnValue=$returnCode\n";
print "output=\n",$output,"\n";

--
[pl>en Andrew] Andrzej Adam Filip : an...@onet.eu : Andrze...@gmail.com
It is far more impressive when others discover your good qualities without
your help.
-- Miss Manners

[Keith Thompson]

Andrzej Adam Filip <andrze...@gmail.com> writes:
[...]

> Use "select" to redirect output of "print without specific file-handle"
> to string (IO::String);
>
> use IO::String;
> my ($returnCode, $output);
> my $io = IO::String->new($output);
> my $oldfh = select($io);
> eval { $returnCode = &blat() };
> select($oldfh);
>
> print "returnValue=$returnCode\n";
> print "output=\n",$output,"\n";

If you have Perl 5.8 or better, you don't need IO::String. Quoting
the IO::String documentation:

Note that perl-5.8 and better has built-in support for "in memory"
files, which are set up by passing a reference instead of a filename to
the open() call. The reason for using this module is that it makes the
code backwards compatible with older versions of Perl.

--
Keith Thompson (The_Other_Keith) ks...@mib.org <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"