Swift

NSDate().timeIntervalSince1970

Go

import (
  "time"
)
int64(time.Now().Unix())

Java

System.currentTimeMillis() / 1000

C

#include <sys/time.h>

// ...
struct timeval tv;
gettimeofday(&tv, NULL);
// 秒： tv.tv_sec
// 毫秒： tv.tv_sec * 1000LL + tv.tv_usec / 1000

JavaScript

Math.round(new Date() / 1000)

Objective-C

[[NSDate date] timeIntervalSince1970]

MySQL

SELECT unix_timestamp(now())
SQLite	
SELECT strftime('%s', 'now')

Erlang

calendar:datetime_to_gregorian_seconds(calendar:universal_time())-719528*24*3600.

PHP

<?php
// pure php
time();

Python

import time
time.time()

Ruby

Time.now.to_i

Shell

date +%s

Groovy

(new Date().time / 1000).longValue()

Lua

os.time()

.NET/C#

DateTimeOffset.UtcNow.ToUnixTimeSeconds();

Dart

(new DateTime.now().millisecondsSinceEpoch / 1000).truncate()