When you start tclsh or wish (on Unix and perhaps a few other platforms) without a filename, you will get a prompt so you can interact with Tcl. (For wish on Windows, use console show instead). If you start them with a filename, that script is executed, but the interactive prompt does not appear.
What if you want both? Donald Porter presented this solution on the comp.lang.tcl newsgroup:
set cmd ""
while 1 {
if { "$cmd" != "" } {
# Why "format catch"? It "is a legacy workaround
# for an old bytcode compiler bug." We should
# find out when it's fixed, and "package require
# Tcl ..." appropriately.
catch {[format catch] $::tcl_prompt2}
} else {
if {[catch {[format catch] $::tcl_prompt1}]} {
puts -nonewline "% "
}
}
flush stdout
append cmd \n[gets stdin]
if [ info complete $cmd ] {
catch $cmd res
puts $res
set cmd ""
}
}Other improvements that could still be made:
Note that the code above is best understood as an improvement on the implementation developed in this Usenet thread: http://groups.google.com/groups?ic=1&th=8a12011a1057f516&seekd=931300072
Benjamin Riefenstahl: That URL doesn't seem to work. Did you mean http://groups.google.com/groups?hl=en&th=79c056a40deb476d&rnum=4 ?
Given the original problem description, the right solution in wish is [console show]. With a little hacking you can have a console for Unix, or better yet, make use of TkCon [L1 ].
For tclsh only, no console widget is available, so then I would go ahead and use [vwait forever] to get an event loop going and use [fileevent stdin readable] to collect and evaluate interactive commands from stdin rather than the [while] loop above.
DGP