Thank you for the prompt reply.
The result of !global --result=ctags-mod -qe 'XXX' was:
global: Command not found.
shell returned 1
The above gave me a hint: I went to the gtags.vim and found that it uses GTAGSGLOBAL.
After setting it, the :Gtags XXX works in vim, but returns bad result:
When running global XXX in the command line, it reported 2 places.
When running Gtags XXX in vim, it reported the same place (the first one) twice.
By the way, now when running !global --result=ctags-mod -qe 'XXX' it still returns the same result.
2012/12/7 Shigio YAMAGUCHI <
address@hidden>
>
> !global --result=ctags-mod -qe 'XXX'