Unix-to-Unix Copy (UUCP) refers to a suite of interfaces and applications used to remotely execute commands and transfer information between networked Unix computers.
UUCP is used to copy information and send commands from one Unix computer system to another. Originally developed in the 1970s and 1980s, UUCP was used extensively to transfer messages and files in local networks over dial-up connections. While UUCP can be used over the Internet, UUCP has largely been superseded by communication protocols like FTP for copying information to web servers, SMTP for handling email, and NNTP for Usenet access.
The UUCP suite includes the following applications and interfaces:
- uucp: A user interface that requests and queues file copying operations between Unix systems.
- uux: An application that sends a command to a Unix system where it is queued for execution.
- uucico: An application that runs at various times throughout the day and initiates the execution of queued uucp (copy) and uux (command execution) requests.
- uuxqt: An application started by the uucico program that executes uux commands.
- uustat: A reporting tool that compiles uucp activity statistics.
- uuname: A program that reports the name of the Unix system making a UUCP activity request.
Frequently Asked Questions
What are some practical examples of the use of UUCP?
In the days before widespread Internet access, UUCP was often used to send email between Unix computers, espeically those connected to a local area network (LAN). Use of UUCP for email outside of a LAN was also possible although less dependable, and messages would often get lost.
The term email address wasn’t used when referring to UUCP messages. Instead, the term bang path was used to describe the addressing system associated with UUCP. Bang paths were also used to direct Usenet traffic when the service was initially launched, and they are still in use within Usenet today, but only for information purposes and not for actual routing of traffic.
If UUCP didn’t use the Internet to connect computers, what did it use?
The network of computers connected through UUCP was called UUCPNET. UUCPNET was a very informal wide area network (WAN) that included thousands of private organizations and universities. UUCP sites were often added to the network without official approval from the top management of the organizations involved, and the system was constantly changing as systems were added and removed.
Gateways between Internet-based SMTP email and UUCP mail were developed, allowing crossover between the two protocols. This infrastructure meant that a UUCP-connected computer could gain access to SMTP email without having to have an Internet connection as long as it was connected by UUCP to a cooperating Internet-connected computer. This arrangement made sense until ISPs became common enough that Internet connections were affordable and widely available, at which point UUCPNET, and the use of UUCP for email and file transfer, declined rapidly.