info level ?number?
If number is not specified, this command returns a number giving the stack level of the invoking procedure, or 0 if the command is invoked at top-level. If number is specified, then the result is a list consisting of the name and arguments for the procedure call at level number on the stack. If number is positive then it selects a particular stack level (1 refers to the top-most active procedure, 2 to the procedure it called, and so on); otherwise it gives a level relative to the current level (0 refers to the current procedure, -1 to its caller, and so on). See the uplevel command for more information on what stack levels mean.
See also:
MGS [2003/09/09] - Note that 'info level 0 does not return values for optional arguments:
proc foo {bar {baz NULL}} {
puts "info level 0 = \[[[[info level 0]]\]]"
}
# example1
foo abc def
# example2
foo abcprints:
info level 0 = [[foo abc def]] info level 0 = [[foo abc]]