From MdsWiki
TCL - Tree Command Language
TCL is a scripting language used for building, browsing or editing trees. It performs many of the same tasks as the TRAVERSER using a command line rather than graphical interface. TCL commands can be invoked as a script or macro or called from applications written in other programming languages. These options are particularly useful for repetitive operations. For example, if a user wishes to store the results of some new analysis on old data, it would be necessary to add new nodes to a large number of old shots. Model trees are often created using TCL scripts, providing self documentation for large, complex structures. If significant changes in the structure are required (not uncommon during development), trees created in this manner can be regenerated after the script has been edited. For example, consider a case where hundreds of nodes are added by a script underneath the current default node. Inserting or modifying a "set default" command will produce wholesale changes that might take hours to carry out one node at a time with the graphical interface.
An index of TCL commands and their functions can be found here.
Some TCL examples can be found here.
Devices, Actions, Events
DEVICES are pre-defined groups of nodes which incorporate setup information, data and task descriptions (ACTIONS). These are generally used for data acquisition and automatic analysis.
ACTIONS are task descriptions which can be defined and executed by MDSplus. These are commonly used in data acquisition DEVICES. A typical data acquisition device will have INIT and STORE actions. Actions are also used for automatic data analysis.
EVENTS are messages which are issued by MDSplus actions or applications. Events are issued by the command SETEVENT and are global in scope. The function WFEVENT will suspend program execution until an event of the appropriate name is heard. Events are used to synchronize data acquisition and analysis. For example, when the event issued by a STORE action is received, it can trigger an analysis job for that data.
SCHEDULING is the process by which all the ACTIONS in an MDSplus tree are collected and organized into a DISPATCH TABLE for subsequent disposition.
DISPATCHING is the process of issuing ACTIONS to SERVERS for execution. 