xev - print contents of X events
xev [-display ''displayname''? [-geometry ''geom''? [-bw ''pixels''? [-bs ''{!NotUseful,!WhenMapped,Always}''? [-id ''windowid''? [-s? [-name ''string''? [-rv?
Xev creates a window and then asks the X server to send it events whenever anything happens to the window (such as being moved, resized, typed in, clicked in, etc.). You can also attach it to an existing window. It is useful for seeing what causes events to occur and to display the information that they contain.
X(7x)?, xwininfo(1)?, xdpyinfo(1)?, Xlib Programmers Manual, X Protocol Specification See X(7x)? for a full statement of rights and permissions.
Jim Fulton, MIT X Consortium
3 pages link to xev(1):