Practical Programming in Tcl & Tk, Third Edition

Reading and Writing

The standard I/O channels are already open for you. There is a standard input channel, a standard output channel, and a standard error output channel. These channels are identified by stdin, stdout, and stderr, respectively. Other I/O channels are returned by the open command, and by the socket command described on page 228.

There may be cases when the standard I/O channels are not available. Windows has no standard error channel. Some UNIX window managers close the standard I/O channels when you start programs from window manager menus. You can also close the standard I/O channels with close.

The puts and gets Commands

The puts command writes a string and a newline to the output channel. There are a couple of details about ...