'''info vars''' ''?pattern?''

If ''pattern'' isn't specified, returns a list of all the names of currently-visible variables. This includes locals and currently-visible globals. If ''pattern'' is specified, only those names matching ''pattern'' are returned. The matching of ''pattern'' is determined using the same rules as for [string match]. ''Pattern'' can be a qualified name like Foo::option*. That is, it may specify a particular namespace using a sequence of namespace names separated by ::s, and may have pattern matching special characters at the end to specify a set of variables in that namespace. If ''pattern'' is a qualified name, the resulting list of variable names has each matching namespace variable qualified with the name of its namespace.

----
Question: in what cases do these two info commands differ?

  set a 1

  set b [info exists a]

and

  set c [info vars a]

The doc for [info exists] indicates
that the variable exists and has a value in either the current or global
space.

Certainly, one potential problem is if the variable has any pattern characters
in it.

Are there other differences between the two?

[MG] May 18th - [[info exists ''varName'']] will return 1 if a variable named varName exists, and 0 if it doesn't. [[info vars ''varName'']] returns a list of all the variables which match the pattern varName. For instance...
 
 1 % set var1 bleh
 bleh
 2 % set var2 bleh
 bleh
 3 % set var3 bleh
 bleh
 4 % info exists var1
 1
 5 % info exists var4
 0
 6 % info vars var1
 var1
 7 % info vars var4
 8 % info exists var*
 0
 9 % info vars var*
 var1 var2 var3
 
[CL] July 18th - There is a difference when the variable exists and has no value. In that case [[info exist ''varName'']] will return 0  whereas [[info vars ''varName'']] will return a list containing ''varName''. For instance...

 1 % namespace eval nspace { variable novalue }
 2 % info exists nspace::novalue
 0
 3 % info vars nspace::novalue
 nspace::novalue

----
See also:

   * [info]
   * [vargrep]

----
[Category Command] - [Tcl syntax help]