Which command would you use to check the current user’s effective user ID?

The command that is used to check the current user’s effective user ID is "whoami." This command provides a straightforward way to display the username of the currently logged-in user. When executed, "whoami" returns the effective user ID (or username), which reflects the user's identity that is currently in effect, especially in contexts where users may have elevated privileges or switch identities using commands like su or sudo. It effectively helps users confirm the identity under which they are operating.

Other commands have different functionalities: the "id" command displays user identity information, including user ID and group IDs, which provides more details than just the effective user ID. The "groups" command lists the groups that the current user belongs to, and "getent" is used to retrieve entries from various data sources like the password database, which isn't specifically focused on displaying the current user’s identity. Thus, "whoami" is the best answer for identifying the effective user ID of the current user.