[Groff] how to format KWIC ptx index and .xx?

[Jeremy C. Reed]

The "Tools for Printing Indexes" report (128.ps) mentions .XX macro from 
index.head for formatting index entries. And it includes a copy of 
index.head at the end of the report.

I am trying to figure out how to make a "keyword-in-context" (KWIC) 
permuted index. (My definition is different than the one in the report 
above.)

It is an alphabetical list of keywords, with some surrounding context. The 
keywords are formatted so they are aligned vertically.

Here is an example of what I have tried:

$ cat J.permutted.1
ypbind(8) ypbind - create and maintain a binding to a NIS server
ypinit(8) ypinit - initialize NIS subsystem
yppoll(8) yppoll - ask version of NIS map from NIS server
yppush(8) yppush - force distribution of NIS map
ypserv(8) ypserv - NIS server daemon
ypset(8) ypset - tell ypbind(8) which NIS server process to use
yptest(8) yptest - calls different NIS routines
ypxfr(8) ypxfr - get a NIS map from NIS server
zdump(8) zdump - time zone dumper
zic(8) zic - time zone compiler

$ gptx -G -r -t -b break -f -w 108 -i ignore J.permutted.1 J.permutted.2

(from coreutils)

$ head -5 J.permutted.2    
.xx "" "yppoll -" "ask version of NIS map from NIS server" "" "yppoll(8)"
.xx "" "ypbind - create and maintain a" "binding to a NIS server" "" "ypbind(8)"
.xx "" "yptest -" "calls different NIS routines" "" "yptest(8)"
.xx "" "zic - time zone" "compiler" "" "zic(8)"
.xx "" "ypbind -" "create and maintain a binding to a NIS server" "" "ypbind(8)"

(By the way, I don't understand why the above is split this way.)

$ groff -ms index.head J.permutted.2 > J.ps

$ head J.ps    
%!PS-Adobe-3.0
%%Creator: groff version 1.19.2
%%CreationDate: Fri Sep 26 15:49:14 2008
%%DocumentNeededResources: font Times-Roman
%%+ font Times-Bold
%%DocumentSuppliedResources: procset grops 1.19 2
%%Pages: 1
%%PageOrder: Ascend
%%DocumentMedia: Default 612 792 0 () ()
%%Orientation: Portrait

J.ps doesn't seem to have anything viewable.

What is a good procedure for this?

Where is a "index.head" I should use?

  Jeremy C. Reed