HEASARC Staff Scientist Position - Applications are now being accepted for a Staff Scientist with significant experience and interest in the technical aspects of astrophysics research, to work in the High Energy Astrophysics Science Archive Research Center (HEASARC) at NASA Goddard Space Flight Center (GSFC) in Greenbelt, MD. Refer to the AAS Job register for full details.

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XPI commands

Some of the commands in Xselect are really a function of the command line interpreter, XPI, and so are common with other HEASARC software like XSPEC and XIMAGE. These are generally commands that give information about the parameters used by Xselect, or do logging of sessions, history recall, etc.

Perhaps the most useful command of the lot is the LPARM command. LPARM Lists the PARameters that a given Xselect command will take, gives a short description of the parameter, and shows its current value.

XPI on UNIX systems uses the GNU READLINE library. This supports full command line editing (including EMACS style commands, e.g. Â for beginning of line Ê for end of line, and Ŝ for incremental search). The up and down arrow keys function for command recall. It does not support the full history mechanism in the READLINE library however, so !! will not recall the previous command, for example. However, XPI also has a built in command recall that supports a similar syntax.

The following are the XPI commands:


  • recall - Recall and replay previous commands
  • alias - Alias complex commands to one word abbreviations
  • script - Open and close script files
  • log - Open and close log files
  • history - Toggles on and off writing to the history file
  • lparm - lists the parameters for a given command
  • ? - lists command groupings
  • ?? - lists the commands available
  • debug - enter debug mode, watch how the command line is parsed
  • dumpkey - dumps the current copy of the key table
  • dumppar - dumps the current (in memory) copy of the par file


The last three of these are really only for debugging

Along similar lines, but actually a part of Xselect, is that for most commands with known range of choices (set device, set instrument, and all the commands of the verb verb_what form), if you wait to be prompted (by hitting a return after the command name), you will be given a list of possible responses, and then prompted for your choice, e.g.: 


xsel >  extract<ret>  

ALL             -->	extract a spectrum, image and light curve
CURVE           --> 	extract a light curve
EVENTS          --> 	output the filtered event list
IMAGE           --> 	extract an image
SPECTRUM        --> 	extract a spectrum
QUIT            --> 	quit extract

> Give parameter to be binned >[all]


In the rest of the section we describe the XPI commands one by one.


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Last modified: Tuesday, 10-Jan-2023 11:03:00 EST

HEASARC Staff Scientist Position - Applications are now being accepted for a Staff Scientist with significant experience and interest in the technical aspects of astrophysics research, to work in the High Energy Astrophysics Science Archive Research Center (HEASARC) at NASA Goddard Space Flight Center (GSFC) in Greenbelt, MD. Refer to the AAS Job register for full details.