xlsatoms

xlsatoms [-display display]

-display display
    This option specifies the X server to connect to. The display argument typically takes the form of hostname:displaynumber.screennumber. If not specified, xlsatoms uses the value of the DISPLAY environment variable.

xlsatoms is a utility for the X Window System that queries an X server and displays a list of all interned atom names and their corresponding integer values. Atoms are unique integer identifiers that the X server uses to represent strings, especially for property names, types, and selection names. This mechanism helps in efficient communication by allowing clients to refer to common strings by their integer IDs rather than transmitting the full string repeatedly.

The command provides a snapshot of these definitions, showing both the human-readable string and its unique numeric ID. It is particularly useful for debugging X applications, understanding the various properties active on an X server, and for developers working with the X protocol who need to inspect the server's internal state regarding these fundamental identifiers.

This command requires a running X server to function properly. The output can be very long depending on the number of interned atoms on the server, which can vary greatly based on running applications and server activity. It is primarily a diagnostic and developer tool and is not typically used for general end-user interaction.

Atoms are a crucial concept in the X Window System protocol. They are unique integer IDs corresponding to strings. When a string (like a property name, type, or selection name) is first used, it is 'interned' by the X server, which assigns it a unique atom ID. Subsequent references to that string then use its atom ID, avoiding the need to transmit the full string data over the network repeatedly. This mechanism helps to optimize network traffic, improve performance, and ensures consistency in named resources across different clients and the server.

xlsatoms is a long-standing utility within the X Window System, originating from early versions of X. It is part of the xorg-x11-utils or similar X.Org utility packages, reflecting its fundamental role in inspecting the server's internal state regarding atom management. Its simple yet powerful function has remained consistent throughout the development of X.

xprop(1), xev(1), xdpyinfo(1), xwininfo(1)