how to recursively grep

[rusi]

I am trying to figure out how to search source trees effectively for
identifiers.
For example I am searching for charset-map-path in the elisp directory
tree

I do
M-x zrgrep
charset-map-path  ;; string searched
... in files: I leave the default as *.gz
Base directory: /usr/share/emacs/23.4/lisp/


-*- mode: grep; default-directory: "/usr/share/emacs/23.4/lisp/" -*-
Grep started at Tue Aug 21 08:35:08

find . \( -path \*/SCCS -o -path \*/RCS -o -path \*/CVS -o -path \*/
MCVS -o -path \*/.svn -o -path \*/.git -o -path \*/.hg -o -path
\*/.bzr -o -path \*/_MTN -o -path \*/_darcs -o -path \*/\{arch\} \) -
prune -o \( -name .\#\* -o -name \*.o -o -name \*\~ -o -name \*.bin -o
-name \*.lbin -o -name \*.so -o -name \*.a -o -name \*.ln -o -name
\*.blg -o -name \*.bbl -o -name \*.elc -o -name \*.lof -o -name \*.glo
-o -name \*.idx -o -name \*.lot -o -name \*.fmt -o -name \*.tfm -o -
name \*.class -o -name \*.fas -o -name \*.lib -o -name \*.mem -o -name
\*.x86f -o -name \*.sparcf -o -name \*.fasl -o -name \*.ufsl -o -name
\*.fsl -o -name \*.dxl -o -name \*.pfsl -o -name \*.dfsl -o -name
\*.p64fsl -o -name \*.d64fsl -o -name \*.dx64fsl -o -name \*.lo -o -
name \*.la -o -name \*.gmo -o -name \*.mo -o -name \*.toc -o -name
\*.aux -o -name \*.cp -o -name \*.fn -o -name \*.ky -o -name \*.pg -o -
name \*.tp -o -name \*.vr -o -name \*.cps -o -name \*.fns -o -name
\*.kys -o -name \*.pgs -o -name \*.tps -o -name \*.vrs -o -name \*.pyc
-o -name \*.pyo \) -prune -o  -type f \( -name \*.gz \) -print0 |
"xargs" -0 -e zgrep -i -nH -e charset-map-path
./cus-start.el.gz:106:       (charset-map-path installation

Grep exited abnormally with code 123 at Tue Aug 21 08:35:29

So it found the occurrence in cus-start.el and stopped abnormally.
Run it a second time and it does finds nothing.

What am I doing wrong?