Perl:

time

PHP:

time()

Ruby:

Time.now.to_i

Python:

import time
int(time.time())

Java:

long epoch = System.currentTimeMillis() / 1000;

C#:

epoch = (DateTime.Now.ToUniversalTime().Ticks - 621355968000000000) / 10000000;

VBScript:

DateDiff("s", "01/01/1970 00:00:00", Now())

Erlang:

calendar:datetime_to_gregorian_seconds(calendar:now_to_universal_time(now())) - 719528*24*3600.

MySQL:

SELECT unix_timestamp(now())

PostgreSQL:

SELECT extract(epoch FROM now());

Oracle:

SELECT (SYSDATE - TO_DATE('01-01-1970', 'DD-MM-YYYY')) * 24 * 60 * 60 FROM DUAL

SQL Server:

SELECT DATEDIFF(s, '1970-01-01 00:00:00', GETUTCDATE())

JavaScript:

Math.round(new Date().getTime() / 1000)

Bash:

date +%s

PowerShell:

Get-Date -UFormat "%s"