Keywords

One of the Keck software infrastructure strengths is the keyword system. All instrument functions should be controllable by keywords. This creates a common interface layer for all instruments. Under normal circumstances, SAs will not need to dive in to the details of the interface protocols for any given component of the instrument (e.g. serial interface, USB interface, etc.).

The two most basic actions one can perform with a keyword are show and modify which report the value of a keyword and change the value respectively. Not all keywords can be modified and some can not show, and a number of the details vary across instruments, but in general, with these two tools one can create any higher level control interface ths is desires (e.g. a script or GUI).

Both show and modify need to be executed with an argument which specifies which service the keyword is in. For example, if I wanted to find out how full the HIRES liquid nitrogen dewar is, I would query the hiccd service for the DWRN2LV keyword value:

By calling show with the -s argument and then specifying the hiccd service and DWRN2LV keyword, I get the information I want. Note, in this example, the DWRN2LV keyword can not be modified.

Another example would be the raw encoder count position of the HIRES cross disperser angle. To view the current position I would query the hires service for the XDRAW keyword:

The XDRAW value is able to be modified. I could do that with the modify command and then verify the final position with show:

Note that while I have followed the convention of writing the service name in lowercase and the keyword name in all caps, this is not necessary as the commands are case insensitive.

There are other commands for keywords:

• xshow will pop up a small window with one or more keywords and their values and will continuously update them. This is basically a very simple status GUI. One can make more complicated xshow instances. For instance, the NIRC2 status display is an xshow. xshow can show keywords from more than one service simultaneously.

• cshow will continuously show the keyword value, printing a new line whenever the value is updated and is a good way to monitor a changing situation. The options for cshow include -timestamp , which will give you a timestamp for the keyword change.

• gshow is not always available, it tends to be installed on newer machines only. It is a more modern and capable version of show and has many options. For services which have a keyword history monitor, gshow can display a history of the keyword values and even generate simple plots of the values over time.