Re^2: Accessing single element without args

The problem here is i can't modify interface_control. It is a global sub which is accessed by many users

@r, has list of routers r[0]....rn, . I want to display output only for r[0] and not for other router

If u see the below code ( under sub interface_control), i want to print blah only for r[0]. If i call interface_control($s), it may end up printing for all routers


  foreach my $rh (@r) {
  print ("blah blah");
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Re^3: Accessing single element without args
by Athanasius (Archbishop) on Mar 31, 2015 at 04:02 UTC

Here is one (inelegant) approach which might work for you:

#! perl
use strict;
use warnings;
use Capture::Tiny ':all';

my ($stdout, $stderr, @result) = capture
{
    interface_control();
};

my    @lines = split "\n", $stdout;
print $lines[0], "\n";

sub interface_control
{
    my @r;
    get_handles(\@r);
    print "blah blah for $_\n" for @r;
}

sub get_handles
{
    @{ $_[0] } = 11 .. 13;
}
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Output:

14:00 >perl 1204_SoPW.pl
blah blah for 11

14:00 >
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Update: Removed unnecessary parentheses from print statement, plus a blank line.

Hope that helps,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

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Re^4: Accessing single element without args

by Anonymous Monk on Mar 31, 2015 at 04:18 UTC

That makes sense :). I will try to use it if my code reviewer approves :)

A final query on my question. As i want to print only r[0], is there a way to set the array @r to only r[0] during interface_control call


push (@r, $r[0])
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I know inside interface_control sub, i can set this, but interface_control can call from outside set this value ?

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Re^5: Accessing single element without args

by Athanasius (Archbishop) on Mar 31, 2015 at 06:09 UTC

No. Your original post shows that @r is created as a lexical variable within sub interface_control. So, even if you could somehow access @r from outside the sub, you would have to do so either:

before the sub is called; in which case any changes you made would be overriden within the sub before the print statement is reached; or
after the sub returns; in which case any changes you made (to a now non-existent variable!) would be too late to affect the printing behaviour.

I’m not familiar with PadWalker, but following Anonymous Monk’s comment above, I had a quick look. As I understand it, PadWalker allows you to access variables in subroutines higher than your current position in the call stack. As you want to access a variable within a subroutine you will be calling, this module won’t help you either. :-(

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

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Re^6: Accessing single element without args

by Anonymous Monk on Mar 31, 2015 at 06:39 UTC

Re^3: Accessing single element without args
by Anonymous Monk on Mar 31, 2015 at 03:49 UTC

Well, then there is nothing you can do, short of doing something foolish like using PadWalker

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