Richard Suchenwirth -- Of course, Tcl's most minimal debugger is puts. But here is a cute little piece of code that offers some more debugging functionality (if you have stdin and stdout available - so not for wish on Windows):
proc bp {{s {}}} { if ![info exists ::bp_skip] { set ::bp_skip [list] } elseif {[lsearch -exact $::bp_skip $s]>=0} return set who [info level -1] while 1 { puts -nonewline "$who/$s> "; flush stdout gets stdin line if {$line=="c"} {puts "continuing.."; break} if {$line=="i"} {set line "info locals"} catch {uplevel 1 $line} res puts $res } }
The idea is that you insert breakpoints, calls to bp, in critical code with an optional string argument (that may be used for distinguishing), like this:
proc foo {args} { set x 1 bp 1 string toupper $args } foo bar and grill
When execution reaches bp, you get a prompt on stdout, giving the calling context and the bp string, like this:
foo bar and grill/1> pwd /home/suchenwi/src/roi/test/mr foo bar and grill/1> i args x foo bar and grill/1> set args bar and grill foo bar and grill/1> set args lowercase lowercase foo bar and grill/1> c
on which you can issue any Tcl command (especially getting or setting variable values in the scope of foo), shorthand commands ("i" for "info locals"; add which others you need), and exit this micro-debugger with "c"(ontinue). Because you modified a local variable, foo's result will be
LOWERCASE
To turn off all breakpoints for an application, just say (maybe from inside bp):
proc bp args {}
You can disable single breakpoints labeled e.g. x with the command
lappend ::bp_skip x
Stepping would be a bigger project, but in some situations a micro-debugger like this is good enough. See also What debugging tools are available to a Tcl programmer