READKEY statement

Reads one keystroke from an input source and sets the value of LASTKEY to the keycode of that keystroke. Use the READKEY statement when you want to look at each keystroke a user makes and take some action based on that keystroke.

Note: Does not apply to SpeedScript programming.
Caution:
If you are executing the READKEY statement while blocking on a .NET main form, a user action can unconditionally shut down the ABL application. For more information, see the WAIT-FOR statement (.NET and ABL) reference entry.

Syntax

READKEY [ STREAM stream | STREAM-HANDLE handle ][ PAUSE n ]
STREAM stream
Specifies the name of a stream. If you do not name a stream, the AVM uses the unnamed stream. See the DEFINE STREAM statement.
STREAM-HANDLE handle
Specifies the handle to a stream. If handle it is not a valid handle to a stream, the AVM generates a run-time error. Note that stream handles are not valid for the unnamed streams. See the chapter on alternate I/O sources in OpenEdge Development: Programming Interfaces for more information on streams and stream handles.
PAUSE n
The READKEY statement waits up to n seconds for a keystroke. You can choose a whole or a fractional value for the time-out interval. If the time-out period you specify is a fractional value, the value is rounded to the nearest whole millisecond. If you do not press a key during that amount of time, READKEY ends, and sets the value in LASTKEY to -1.

PAUSE 0 causes READKEY to immediately return a value. If no character is available, READKEY sets the value of LASTKEY to -1. Use this form of READKEY to do polling through UNIX pipes or terminal ports.

Example

In the following procedure, when the user presses a key, the READKEY statement reads the keystroke and stores the character code value of that key (the key code) as the value of LASTKEY. The CHR function converts the character code value into a character value. If the character value is a Y, the AVM deletes the Customer. KEYFUNCTION determines the function of the LASTKEY. If that function is END-ERROR, the AVM exits the block, ending the procedure.

r-readky.p

FOR EACH Customer:
  DISPLAY Customer.CustNum Customer.Name Customer.Address Customer.City 
    Customer.State WITH 1 DOWN.
  MESSAGE "If you want to delete this customer, press Y".
  MESSAGE "Otherwise, press any other key.".
  READKEY.
  IF CHR(LASTKEY) = "Y" THEN DELETE Customer.
  ELSE IF KEYFUNCTION(LASTKEY) = "END-ERROR" THEN LEAVE.
END.

Notes

See also

DEFINE STREAM statement, EDITING phrase, LASTKEY function, Stream object handle