'''info exists''' ''varName''

Returns '''1''' if the variable named ''varName'' exists in the current context (either as a global or local variable) and has been defined by being given a value, returns '''0''' otherwise.

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See also:

   * [info]

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Called with a variable or array element name (no $ in front!), returns 1 if the variable or array element exists, else 0.

  info exists a
 0
  set a 1
 1
  info exists a
 1
  info exists b
 0
  set b(2) 2
 2
  info exists b
 1
  info exists b(1)
 0
  info exists b(2)
 1
  info exists $a
 0

Notice the last one - if the user thought they were testing to see if the
a variable exists, they used the wrong syntax - saying $a means ''read
the contents of the a variable, and see if there is a varible by
that name.''

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[Category Command] -
[Tcl syntax help]