xshow is a simple tool for displaying continually updating values of keywords. It can also display keyword values graphically as a function of time. It is commonly used for updating text displays of important parameters for either the telescope subsystems or instruments.

Text Displays

To display keyword values in a text format, use the form

xshow -s service key1 key2 key3 key4 key5

where service is the service name or keyword library name, such as "lris", "dcs", "ao", or "nirc". This is the same format as "modify" and "show" command access to keyword libraries. "key1" through "key5" are keywords within this library.

As an example, the following shows a DCS xshow screen, displaying RA, Dec, UTC, and various other useful parameters:

This was invoked by the command

    xshow -s dcs lst ut ha ra dec airmass \
    poname targname axestat telfocus secfocus tubetemp domeposn az el parang \
    rotpposn rotposn
Note that the left column contains the keyword name, and the right column contains the value; the same information seen if you were to type "show -s dcs lst", except that the show command may have additional comments such as units after the value.

Also note that the two columns are always forced to have the same width. Very long keyword names or (more likely) values will force the window to resize to a large width, potentially with a lot of wasted white space.

The flag "-twocol" can be used to create a four-column (despite the flag name!) list, two columns each of (name, value) pairs. The end of this Web page discusses other command-line options.

Graphical Displays

xshow can alternatively display a time series of one keyword value.

Need an example and image.

Common Command-Line Options


xshow [-serv service_name].. [-twocol] [-noprime] [-nohead] [-noquit] [-histo [-aut]] keywords
-serv service      defines the service or keyword library.
This is REQUIRED. It is possible to define more than one service name, and include keywords from both services. This may impact performance and stability of the xshow, however, and is generally avoided.
-twocol      uses two columns of (name, value) pairs, rather than one.
-noprime      xxx
-nohead      xxx
-noquit      removes the "quit" button from the xshow display.
-histo      defines the window as a graphical display. Generally a number of X resources must then be defined as "-xr "resource: value" as shown below.
-aut      xxx
-xr "xshow*srows*fontList: 10x20"      defines a font size, in this case 10x20 pixels, for a text display.
-xr "xshow*trend.max0: 200"      defines the maximum y-axis value for a graphical display. In this case it is 200.
-xr "xshow*trend.min0: 0"      defines the minimum y-axis value for a graphical display. In this case it is 0.
-xr "xshow*trend.timeBase: 3600"      defines the length of the timeline in seconds for a graphical display. In this case the last 3600 seconds of time will be shown.
-ti title      defines a title for the window. Strings with spaces and special characters must be enclosed in quotes.
-n icon-name      sets the name displayed under the icon when the xshow window is iconified.