Tclx documents commandloop as:
commandloop ?-async? ?-interactive on | off
Create an interactive command loop reading commands from
stdin and writing results to stdout. Command loops are maybe
either be blocking or event oriented. This command is useful
for Tcl scripts that do not normally converse interactively
with a user through a Tcl command interpreter, but which
sometimes want to enter this mode, perhaps for debugging or
user configuration. The command loop terminates on EOF.
The following options are available:
-async
A command handler will be associated with stdin. When
input is available on stdin, it will be read and
accumulated until a full command is available. That
command will then be evaluated. An event loop must be
entered for input to be read and processed.
-interactive on | off | tty
Enable or disable interactive command mode. In
interactive mode, commands are prompted for and the
results of comments are printed. The value maybe any
boolean value or tty. If tty is used, interactive mode
is enabled if stdin is associated with a terminal or
terminal emulator. The default is tty.
-prompt1 cmd
If specified, cmd is used is evaluate and its result
used for the main command prompt. If not specified, the
command in tcl_prompt1 is evaluated to output the prompt.
Note the difference in behavior, cmd results is used,
while tcl_prompt1 outputs. This is to allow for future
expansion to command loops that write to other than
stdout.
-prompt2 cmd
If specified, cmd is used is evaluate and its result used
for the secondary (continuation) command prompt. If not
specified, the command in tcl_prompt2 is evaluated to
output the prompt.
-endcommand cmd
If specified, cmd is evaluated when the command loop
terminates.
In interactive mode, the results of set commands with two
arguments are not printed.
If SIGINT is configured to generate a Tcl error, it can
be used to delete the current command being type without
aborting the program in progress.KBK 2004-05-18 - Something very similar can be done in pure Tcl; the signal handling and 'isatty' checking is Unix and hence unportable, but the following code works for many purposes:
namespace eval ::mainloop {
variable partialCommand {}
}
proc ::mainloop::prompt {} {
variable partialCommand
if { [info complete $partialCommand] } {
set status [catch {
uplevel \#0 $partialCommand
} result]
if { $result ne {} } {
if { $status != 0 } {
puts stderr $result
} else {
puts stdout $result
}
}
set partialCommand {}
if { [info exists ::tcl_prompt1] } {
catch { uplevel \#0 $::tcl_prompt1 } prompt
} else {
set prompt "% "
}
} else {
append partialCommand \n
if { [info exists ::tcl_prompt2] } {
catch { uplevel \#0 $::tcl_prompt2 } prompt
} else {
set prompt "> "
}
}
puts -nonewline stderr $prompt
return
}
proc ::mainloop::readable {} {
variable partialCommand
variable eof
if { [gets stdin text] < 0 } {
fileevent stdin readable {}
set eof 1
} else {
append partialCommand $text
prompt
}
return
}
proc ::mainloop::mainloop {} {
variable eof
set ::tcl_interactive 1
info script ""
fconfigure stdin -buffering line -blocking 0
fileevent stdin readable ::mainloop::readable
::mainloop::prompt
vwait [namespace which -variable eof]
return
}
::mainloop::mainloopCategory Command, a part of Tclx