XPACmdNew(3) create a new XPA public access point for commands


#include <xpa.h>
XPA XPACmdNew(char *class, char *name);


Create a new XPA public access point for commands that will share a common identifier class:name. Enter this access point into the XPA name server, so that it can be accessed by external processes. XPACmdNew() returns an XPA struct.

It often is more convenient to have one public access point that can manage a number of commands, rather than having individual access points for each command. For example, it is easier to command the ds9 image display using:

  echo "colormap I8"   | xpaset ds9
  echo "scale log"     | xpaset ds9
  echo "file foo.fits" | xpaset ds9

then to use:

  echo "I8"       | xpaset ds9_colormap
  echo "log"      | xpaset ds9_scale
  echo "foo.fits" | xpaset ds9_file

In the first case, the commands remain the same regardless of the target XPA name. In the second case, the command names must change for each instance of ds9. That is, if a second instance of ds9 called DS9 were running, it would be commanded either as:

  echo "colormap I8"   | xpaset DS9
  echo "scale log"     | xpaset DS9
  echo "file foo.fits" | xpaset DS9

or as:

  echo "I8"       | xpaset DS9_colormap
  echo "log"      | xpaset DS9_scale
  echo "foo.fits" | xpaset DS9_file

Thus, in cases where a program is going to manage many commands, it generally is easier to define them as commands associated with the XPACmdNew() routine, rather than as separate access points using XPANew().

When XPACmdNew() is called, only the class:name identifier is specified. Each sub-command is subsequently defined using the XPACmdAdd() routine.