The Linux command groups can be used to determine the list of groups a specific user belongs to. This should work in almost all flavors of Linux distributions. The following example shows how to use it.

[neo@techpulp ~]# groups
engineers devel
[neo@techpulp ~]# groups neo
engineers devel
[neo@techpulp ~]# groups liz
engineers qa
[neo@techpulp ~]#