- getegid - get the effective group ID
- getgid - get the real group ID
- getgrgid, getgrgid_r - get group database entry for a group ID
- getpgid - get the process group ID for a process
- setegid - set the effective group ID
- setgid - set-group-ID
- setpgid - set process group ID for job control
- setregid - set real and effective group IDs