How to find out files with unkown user name and group name?

[Zhang Zhao gui]

I want to change the ownership and group name for those
orphaned files without specified name in /etc/passwd (they are displayed as
unknown numbers)
I can use "find -user +300 -exec ls -l {} \; " to find
out those files with unknown user ID but cannot
do the same thing for those files with unknown group ID. Because "find -group
+300 -exec ls -l {} \; " will
not work. Anybody got any idea?

[Vitek Pepas_1]

You want to find all files with numbers instead of user id, so use script
similar to following as an argument of -exec option.

find . -exec check_user {} \;

check_user:

#/usr/bin/ksh
ls -l $1 | read RERM LINKS USER GROUP THEREST
[[ $USER = [0-9][0-9][0-9] ]] && echo "$1 - user unknown: $USER"

Add corresponding line for checking group id.

[Zhang Zhao gui]

I think it will not work if I put check_user into the same script as where find
command is and call it as a
subroutine "check_user()". I can only get it done
after I put check_user in a separate script file and
specify the pathname after "find -exec", that is,
find -exec /tmp/check_user {} \;

But it is very slow. I found a better solution by using "-nouser" or "nogroup"
option in "find" command.