List all global variables

Question

As noted elsewhere, you can list all user-defined symbols with this:

Names["Global`*"]

But I'd like to find just my global variables (I'm in the middle of some hairy debugging), not my function definitions. Something like this is close:

Select[Names["Global`*"], Head@Symbol[#]=!=Symbol && Head@Symbol[#]=!=Function&]

But that misses variables whose value is a symbol (perhaps I have x = Pi).

I could probably beat that thing into submission but maybe there's a cleaner, more direct way?

Answer 1

If we consider any symbol with an own-value as a "variable", then this will do the trick:

ClearAll[variableQ]
variableQ[name_String] := {} =!= ToExpression[name, InputForm, OwnValues]

Select[Names["Global`*"], variableQ]

Note that this technique will fail on read-protected symbols and will misidentify some forms of auto-loaded functions.

Edit 1

As @Szabolcs points out, the definition of variableQ can be simplified if ValueQ is used:

variableQ[name_String] := ToExpression[name, InputForm, ValueQ]

Edit 2

As @dreeves points out, it might be desirable to filter out apparent variables whose values are functions, e.g. f = (#+1)&:

variableQ[name_String] :=
  MatchQ[
    ToExpression[name, InputForm, OwnValues]
  , Except[{} | {_ :> (Function|CompiledFunction)[___]}]
  ]

This definition could be easily extended to check for other function-like forms such as interpolating functions, auto-loaded symbols, etc.