usage: /usr/bin/xmessage [-options] [message ...]

where options include:
    -file filename              file to read message from, "-" for stdin
    -buttons string             comma-separated list of label:exitcode
    -default button             button to activate if Return is pressed
    -print                      print the button label when selected
    -center                     pop up at center of screen
    -nearmouse                  pop up near the mouse cursor
    -timeout secs               exit with status 0 after "secs" seconds