Screen

.screenrc:
hardstatus alwayslastline "%{+b rk}%H%{gk} %c %{yk}%d.%m.%Y  %?%{wk}%-Lw%?%{gk}%n*%f %t%?(%u)%?%?%{wk}%+Lw%?%{yk}%84=Load: %l %{wk}"

screen -ls
screen
screen -x : show attached
screen -d : detach
screen -r : reattach

^a c  : new window
^a ^a : toggle windows
^a 1  : show window #1
^a A  : rename window

Reset root password for PostgreSQL

EITHER:

$ ps -ef | grep postgres

postgres  3940     1  0 12:38 ?        00:00:00 /usr/lib/postgresql/8.4/bin/postgres -D /var/lib/postgresql/8.4/main -c config_file=/etc/postgresql/8.4/main/postgresql.conf

$ grep 'hba_file' /etc/postgresql/8.4/main/postgresql.conf

hba_file = '/etc/postgresql/8.4/main/pg_hba.conf' # host-based authentication file

# vi /etc/postgresql/8.4/main/pg_hba.conf

OR:

# vi $(grep 'hba_file' $(ps -ef | grep postgres | awk '{ if ( $3 == 1 ) print $NF }' | cut -d '=' -f 2) | cut -d "'" -f 2)

#local all postgres md5
local all postgres trust

# service postgresql-8.4 restart

# su - postgres

$ psql -d template1 -U postgres

> alter user postgres with password 'new_password';

# vi /etc/postgresql/8.4/main/pg_hba.conf


OR:

# vi $(grep 'hba_file' $(ps -ef | grep postgres | awk '{ if ( $3 == 1 ) print $NF }' | cut -d '=' -f 2) | cut -d "'" -f 2)


local all postgres md5
#local all postgres trust

# service postgresql-8.4 restart

$ psql -d template1 -U postgres

Efficient splitting every 3 digits

my $num = 12_345_678;
$num = reverse $num;
$num = reverse join( ' ', grep( $_, split( /(...)/g, $num ) ) );
# $num = '12 345 678';

UTF8

# flags source code as UTF8
use utf8;

# flags STDOUT as UTF8
binmode(STDOUT, ":encoding(utf-8)");

Stop "sshd" in Ubuntu

Internet says this one works: 
sudo update-rc.d -f sshd remove

but  it isn't.
It does NOT work.
The following works: 
sudo apt-get remove openssh-server

Real UID vs Effective UID

If you think about a large company where employees have different levels of access to different locations, you could compare the Real User ID to the name badges people wear, and the Effective User ID to the set of keys they've been given.

Perl module version

perl -MDateTime -le 'print DateTime->VERSION'

OR:

pmvers DateTime