screen: At

 
 20.1 At
 =======
 
  -- Command: at [identifier][#|*|%] command [args]
      (none)
      Execute a command at other displays or windows as if it had been
      entered there.  'At' changes the context (the 'current window' or
      'current display' setting) of the command.  If the first parameter
      describes a non-unique context, the command will be executed
      multiple times.  If the first parameter is of the form
      'IDENTIFIER*' then identifier is matched against user names.  The
      command is executed once for each display of the selected user(s).
      If the first parameter is of the form 'IDENTIFIER%' identifier is
      matched against displays.  Displays are named after the ttys they
      attach.  The prefix '/dev/' or '/dev/tty' may be omitted from the
      identifier.  If IDENTIFIER has a '#' or nothing appended it is
      matched against window numbers and titles.  Omitting an identifier
      in front of the '#', '*' or '%' character selects all users,
      displays or windows because a prefix-match is performed.  Note that
      on the affected display(s) a short message will describe what
      happened.  Note that the '#' character works as a comment
      introducer when it is preceded by whitespace.  This can be escaped
      by prefixing '#' with a '\'.  Permission is checked for the
      initiator of the 'at' command, not for the owners of the affected
      display(s).  Caveat: When matching against windows, the command is
      executed at least once per window.  Commands that change the
      internal arrangement of windows (like 'other') may be called again.
      In shared windows the command will be repeated for each attached
      display.  Beware, when issuing toggle commands like 'login'!  Some
      commands (e.g.  '\*Qprocess') require that a display is associated
      with the target windows.  These commands may not work correctly
      under 'at' looping over windows.