Setting environment variable globally without restarting Ubuntu

Question

I know that system wide environment variables can be set by adding entries into

/etc/environment

or

/etc/profile

Answer 1

This perl program uses gdb to change the USER variable in all currently running bash shells to whatever is given as the program arg. To set a new variable the internal bash call "set_if_not" could be used

#!/usr/bin/perl

use strict;
use warnings;

my @pids = qx(ps -C bash -o pid=);
my $foo  = $ARGV[0];
print "changing user to $foo";
print @pids;

open( my $gdb, "|gdb" ) || die "$! gdb";
select($gdb);
$|++;
for my $pid ( @pids ) {
    print "attach $pid\n";
    sleep 1;
    print 'call bind_variable("USER","' . $foo . '",0)' . "\n";
    sleep 1;
    print "detach\n";
}

This only works with bash ( I only tested it with version 4.1 on Ubuntu 10.04 LTS) and does not alter the environment for arbitrary already running programs. Obviously it must be run as root.