'''`[namespace] upvar`''' creates an alias to a namespace variable.



** Synopsis **

    :   '''namespace upvar''' ''namespace otherVar myVar'' ?''otherVar myVar ...''?



** Description **

Resolves a variable named ''otherVar', which may contain [namespace%|%namespace
qualifiers], ' relative to ''namespace'' and gives it the name ''myVar'', which
also my contain [namespace qualifiers], in the current [level].  It is the same
variable regardless of which name its value is read or stored through.

`namespace upvar` is a convenience command that doesn't add any functionality
not previously available with `[upvar]`.  The following are equivalent:

======
set ns ::foo
upvar #0 ${ns}::bar boo
======

and

======
set ns ::foo
namespace upvar $ns bar boo
======

However, the second form is more efficient as it requires less string manipulation and parsing.


In contrast to `[variable]` `namespace upvar` provides the ability to give the
variable an arbitrary name :

======
proc myproc {} {
    variable var1
    namespace upvar [namespace current] var1 myvar1
}
======





[DKF]: `namespace upvar` was created to help accelerate [Snit].



** See Also **

   [namespace]:   the primary command for working with namespaces

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