console - Control the console on systems without a real console
console subcommand ?
arg ...?
The console window is a replacement for a real console to allow input and output
on the standard I/O channels on platforms that do not have a real console. It
is implemented as a separate interpreter with the Tk toolkit loaded, and
control over this interpreter is given through the
console command. The
behaviour of the console window is defined mainly through the contents of the
console.tcl file in the Tk library. Except for TkAqua, this command is
not available when Tk is loaded into a tclsh interpreter with “
package require Tk”, as a conventional terminal is expected to
be present in that case. In TkAqua, this command is disabled when there is a
startup script and stdin is
/dev/null (as is the case e.g. when a
bundled application embedding Tk is started by the macOS Launcher). To enable
the command in that case, define the environment variable
TK_CONSOLE.
This can be done by modifying the Info.plist file by adding the LSEnvironment
key to the main dict and setting its value to be a dict with the key
TK_CONSOLE.
-
console eval script
- Evaluate the script argument as a Tcl script in the
console interpreter. The normal interpreter is accessed through the
consoleinterp command in the console interpreter.
- console hide
- Hide the console window from view. Precisely equivalent to
withdrawing the . window in the console interpreter.
- console show
- Display the console window. Precisely equivalent to
deiconifying the . window in the console interpreter.
-
console title ?string?
- Query or modify the title of the console window. If
string is not specified, queries the title of the console window,
and sets the title of the console window to string otherwise.
Precisely equivalent to using the wm title command in the console
interpreter.
The
consoleinterp command in the console interpreter allows scripts to be
evaluated in the main interpreter. It supports two subcommands:
eval
and
record.
-
consoleinterp eval script
- Evaluates script as a Tcl script at the global level
in the main interpreter.
-
consoleinterp record script
- Records and evaluates script as a Tcl script at the
global level in the main interpreter as if script had been typed in
at the console.
There are several additional commands in the console interpreter that are called
in response to activity in the main interpreter.
These are documented here
for completeness only; they form part of the internal implementation of
the console and are likely to change or be modified without
warning.
Output to the console from the main interpreter via the stdout and stderr
channels is handled by invoking the
tk::ConsoleOutput command in the
console interpreter with two arguments. The first argument is the name of the
channel being written to, and the second argument is the string being written
to the channel (after encoding and end-of-line translation processing has been
performed.)
When the
. window of the main interpreter is destroyed, the
tk::ConsoleExit command in the console interpreter is called (assuming
the console interpreter has not already been deleted itself, that is.)
The default script creates a console window (implemented using a text widget)
that has the following behaviour:
- [1]
- Pressing the tab key inserts a TAB character (as defined by
the Tcl \t escape.)
- [2]
- Pressing the return key causes the current line (if
complete by the rules of info complete) to be passed to the main
interpreter for evaluation.
- [3]
- Pressing the delete key deletes the selected text (if any
text is selected) or the character to the right of the cursor (if not at
the end of the line.)
- [4]
- Pressing the backspace key deletes the selected text (if
any text is selected) or the character to the left of the cursor (of not
at the start of the line.)
- [5]
- Pressing either Control+A or the home key causes the cursor
to go to the start of the line (but after the prompt, if a prompt is
present on the line.)
- [6]
- Pressing either Control+E or the end key causes the cursor
to go to the end of the line.
- [7]
- Pressing either Control+P or the up key causes the previous
entry in the command history to be selected.
- [8]
- Pressing either Control+N or the down key causes the next
entry in the command history to be selected.
- [9]
- Pressing either Control+B or the left key causes the cursor
to move one character backward as long as the cursor is not at the
prompt.
- [10]
- Pressing either Control+F or the right key causes the
cursor to move one character forward.
- [11]
- Pressing F9 rebuilds the console window by destroying all
its children and reloading the Tcl script that defined the console's
behaviour.
Most other behaviour is the same as a conventional text widget except for the
way that the
<<Cut>> event is handled identically to the
<<Copy>> event.
Not all platforms have the
console command, so debugging code often has
the following code fragment in it so output produced by
puts can be
seen while during development:
destroy(3tk),
fconfigure(3tcl),
history(3tcl),
interp(3tcl),
puts(3tcl),
text(3tk),
wm(3tk)
console, interpreter, window, interactive, output channels