NAME
checkgid – validate group identifiers
SYNOPSIS
checkgid group ...
DESCRIPTION
Given one or more group identifers on the command line (e.g., "httpd" or "#-1"), figure out whether they'll be valid for the server to use at run-time.
If a groupname isn't found, or we can't setgid() to it, return -1. If all groups are valid, return 0.
This may need to be run as the superuser for the setgid() to succeed; running it as any other user may result in a false negative.