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



** Synopsis **

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



** Description **

'''`[namespace] upvar`''' links ''otherVar'' to ''myVar'' at the current
[level], after which an operation on ''otherVar'' is identical to the same
operation on ''myVar'', and vice versa.  ''otherVar'' is resolved relative to
''namespace'', and may contain [namespace%|%namespace qualifiers].  ''myVar'' is resolved relative to the current level, and may also contain [namespace qualifiers].

`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 at the time the link is made, as it requires less string manipulation and parsing.


`namespace upvar` can be used in as a form of `[variable]` that provides the
ability name the variable something else at the current level:

======
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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