How to send sms programmatically?

The articles listed below may be useful:
Are there any free services for sending SMS programmatically?
[Programmatic SMS] [3]
[Free SMS API?] [4]

EDIT Removed first link that has been removed

I use an SMS gateway and it is fairly easy but I did consider this as an alternative because it potentially gave me more control email to sms

Send an email to the 10 digit phone number @ Carrier's domain name.

Here is a list of the carriers and their domains:

https://en.wikipedia.org/wiki/List_of_SMS_gateways