Which psql meta-command is used to display all roles and their attributes?

The \du meta-command in psql is used to list all available roles. Since PostgreSQL version 8.1, the concepts of "users" and "groups" have been unified into a single entity type called a "role". Therefore, \du displays all roles, which encompasses what were formerly known as users and groups. The output includes the role name and a list of its attributes, such as Superuser, Create role, Create DB, Connections, and membership in other roles. The \du command is an alias for \dg, providing identical functionality.

\dr: This is not a valid psql meta-command for listing roles. The \drds command exists to show default access privileges, but \dr is not a defined command.

\roles: This is not a valid psql meta-command. Meta-commands must begin with a backslash (\). ROLES is a SQL identifier, not a client command.

\users: This is not a valid psql meta-command. Like \roles, it lacks the required backslash prefix and is not a defined psql command.

1. PostgreSQL 16 Documentation, psql Meta-Commands: The official documentation lists \du and its alias \dg as the commands to "list roles". The table explicitly describes its function.

Source: PostgreSQL 16 Documentation, Section: psql, Subsection: "Meta-Commands". The table under the "Informational" category lists \du[S+] [pattern] with the description "list roles".

2. PostgreSQL 16 Documentation, Database Roles: This section clarifies the unification of users and groups into roles, which is fundamental to understanding why \du lists all of them.

Source: PostgreSQL 16 Documentation, Chapter 22: "Database Roles", Section 22.1: "Database Roles". The first paragraph states, "PostgreSQL manages database access permissions using the concept of roles. A role can be thought of as either a database user, or a group of database users... Since version 8.1, users and groups are unified into a single kind of entity called a role."