Practical Programming in Tcl & Tk, Third Edition

The fileevent Command

The fileevent command registers a procedure that is called when an I/O channel is ready for read or write events. For example, you can open a pipeline or network socket for reading, and then process the data from the pipeline or socket using a command registered with fileevent. The advantage of this approach is that your application can do other things, like update the user interface, while waiting for data from the pipeline or socket. Network servers use fileevent to manage connections to many clients. You can use fileevent on stdin and stdout, too. Using network sockets is described in Chapter 17.

The command registered with fileevent uses the regular Tcl commands to read or write data on the I/O channel. For example, ...