$ id -u
1000
$ id -g
1000

$ /tmp/k
Current Effective User ID: 0
Current Effective Group IDs: 1000 1002 1001 1000
Requested User ID: 1001
Requested Group ID: 55
Changing Effective IDs
Current Effective User ID: 1001
Current Effective Group IDs: 55 1002 1001 1000