56.3. Writing an event orderer startup script

This section provides skeletal information that should guide you in writing your own event orderer startup script. If you actually decide to take that plunge you'll want to look at the reference material in 1evb. You'll also want to look at the next section which provides a broad brush overview of the user interface elements provided with the software.

The best way to get an feel for what you need to do is to look at the standard startup script as of the time this document was written:

Example 56-1. The standard startup script explained

# Start Tclsh \                             (1)
exec tclsh8.5 ${0} ${@}

lappend auto_path [file join /usr/opt/daq/10.2 TclLibs] (2)

package require EventBuilder
package require EVB::connectionList      (3)
package require EVB::GUI


if {$argc > 0} {
    EVB::Start [lindex $argv 0]
} else {

EVB::createGui .test
pack .test                             (5)

EVB::maintainGUI .test                 (6)

This is a standard Tcl trick to start up the Tcl interpreter. Note that the actual version of Tcl to start is determined by the NSCLDAQ installer and is normally the highest version installed in a 'standard location'. This magic incantation gets around issues that can occur if Tcl is not enabled as a system shell.

If you have the Tcl documentation installed on your system do a man tclsh and read the section SCRIPT FILES. Note that the example in that section is for the sh shell rather than bash and that acounts for the minor syntactical differences.

The NSCLDAQ auto configuration/installer modifies this line as well. The purpose of the line is to add the NSCLDAQ Tcl package library directory tree to the set of paths that are searched for packages by the package require command.

This is done because the event builder/event orderer software is basically a set of Tcl packages.

This set of lines loads the packages that make up the event builder/orderer and its user interface:


Provides a set of procedures in the EVB:: namespace that support setting up and controlling the event builder/orderer.


This package provides code that implements a list of the clients connected to the server component of the event orderer.


The user standard user interface components.

Does everything needed to start the event orderer package. Note that the first command parameter, if present is passed as an optional parameter to the EVB::Start as the name of the event builder. Once started you have a pair of choices:

  • Enter the event loop via a vwait command. The event builder is event driven and entering the event loop ensures events a delivered to the correct components.

  • Load Tk directly or indirectly as that installs an event loop in the application.

The command EVB::createGui .test creates the event orderer's default user interface/monitoring interface. .test is the name of the uppermost window of the user interface. If you are doing a custom script, you could incorporate this in with your user interface by e.g. creating a frame and specifying the name of a window that would live inside of the frame.

The pack command makes the standard user interface visible inside its parent window (in this case the initial top level window .).

Starts an after rescheduling procedure that fetches statistics from the orderer and updates the appropriate chunks of the user interface.

In general the part that is mutable is going to be what, if any hooks you make use of after starting the event orderer and how you handle the user interface an its maintenance. Refer to the reference section for more information about the hooks that area available and how to make use of them.