libuser-lid

View documentation for the original command

$ tldr lid.libuser

libuser-lid [-u|-g] NAME_OR_ID
libuser-lid -V

-u
    Specify that the lookup should be for a user. This is the default behavior if neither -u nor -g is provided.

-g
    Specify that the lookup should be for a group.

-V
    Display the version information for the libuser-lid command and exit.

NAME_OR_ID
    The user or group name (e.g., 'root', 'users') or numerical ID (e.g., '0', '1000') to be resolved. The command determines if it's a name or an ID and performs the appropriate lookup.

The libuser-lid command is a utility from the libuser library, designed for mapping user and group identifiers. Its primary function is to translate user or group names into their corresponding numerical IDs (UIDs for users, GIDs for groups), and conversely, to resolve numerical IDs back into their respective names. This command serves as a low-level interface for applications that need to look up or verify user and group information within the system's authentication databases, such as /etc/passwd, /etc/group, and potentially other sources configured through NSS (Name Service Switch). It is an essential component for programs built upon the libuser framework, enabling them to handle user and group attributes consistently and efficiently. It aids in scripting and debugging tasks where direct ID-to-name or name-to-ID lookups are required without parsing system files directly.

This utility is primarily found on systems utilizing the libuser library for user and group management, such as Red Hat Enterprise Linux and Fedora. Its effectiveness depends on the system's Name Service Switch (NSS) configuration to correctly query various user and group databases (e.g., /etc/passwd, LDAP, NIS). It exits with a non-zero status upon failure to resolve an identifier.

The libuser-lid command exits with 0 on success (identifier found and displayed) and a non-zero value if the identifier cannot be resolved or an error occurs (e.g., invalid arguments).

To find the UID of user 'john':
libuser-lid john

To find the GID of group 'developers':
libuser-lid -g developers

To find the name of the user with UID 1000:
libuser-lid 1000

To find the name of the group with GID 500:
libuser-lid -g 500

The libuser-lid command is an integral part of the libuser project, a library developed by Red Hat to provide a standardized, consistent, and extensible API for managing user and group accounts on Linux systems. It emerged from the need for robust and reliable tools that could abstract the complexities of various underlying account databases (like /etc/passwd, LDAP, NIS), allowing applications to interact with user and group information uniformly. The libuser framework and its associated utilities like libuser-lid have been a core component of Red Hat-based distributions for many years, simplifying user management for system administrators and developers alike.

libuser(3), getent(1), id(1), useradd(8), groupadd(8)