The TCL language __linux in Linux

Tcl (the earliest known as "tool Command Language", "Tool command Language", but this is not the meaning, but we still call it tcl) is a scripting language. Created by John Ousterhout. Tcl is very studious and powerful. Tcl is often used for rapid prototyping, scripting, GUI and testing. Tcl reads "Kicking" and "tickle". The characteristics of TCL include:

* Everything is a command, including a syntax structure (for, if, and so on).

* Everything can be redefined and overloaded.

* All data types can be considered as strings.

* Grammar rules are fairly simple

* Provides event driven to sockets and files. Time based or user-defined events are also possible.

* Dynamic domain definition.

* Easy to use C, C + +, or Java extensions.

* Explain the language, the code can change dynamically.

* Full Unicode support.

* Platform Independent. Win32, UNIX, can run on a Mac.

* Tightly integrated with the GUI of Windows.

* Code is compact and easy to maintain.

TCL itself does not provide object-oriented support. But the language itself can easily be extended to support object-oriented objects. Many C language extensions provide object-oriented capabilities, including XOTCL, INCR Tcl and so on. In addition Snit expansion itself is written in Tcl.

The most widely used TCL extension is TK. TK provides a graphical user interface GUI for a variety of OS platforms. Even the powerful Python language does not provide its own GUI alone, but rather provides an interface to fit on TK. Another popular expansion pack is expect. Expect provides the ability to automate commands via a terminal, such as (passwd, FTP, Telnet, etc.).

Tcl is widely used in the script language, and in most cases, Tcl and TK ("Tool Kit") libraries are in use simultaneously, and TK is a series of commands and procedures that allow TCL to easily write graphical user interfaces

An important feature of TCL is its extensibility. If a program needs to use some standard TCL does not provide the functionality, you can use the C language to create some new TCL commands, and easy integration. It is because TCL is easy to expand that many people write expansion packs for it and share them online.

TCL differs from other programming languages such as C, which is an interpretation language rather than a compiled language. The TCL program consists of a series of TCL commands, which are run by the TCL interpreter at run time. One of the advantages of running is that it can generate TCL script for itself.

The vast majority of TCL's input/output is done through puts and gets. The puts command is displayed on the console, and the gets command obtains the data from the console input and stores it in a variable.