variable

variable(3tcl)                Tcl Built-In Commands               variable(3tcl)



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NAME
       variable - create and initialize a namespace variable

SYNOPSIS
       variable name

       variable ?name value...?
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DESCRIPTION
       This command is normally used within a namespace eval command to create
       one or more variables within a namespace.  Each variable name is
       initialized with value.  The value for the last variable is optional.

       If a variable name does not exist, it is created.  In this case, if value
       is specified, it is assigned to the newly created variable.  If no value
       is specified, the new variable is left undefined.  If the variable
       already exists, it is set to value if value is specified or left
       unchanged if no value is given.  Normally, name is unqualified (does not
       include the names of any containing namespaces), and the variable is
       created in the current namespace.  If name includes any namespace
       qualifiers, the variable is created in the specified namespace.  If the
       variable is not defined, it will be visible to the namespace which
       command, but not to the info exists command.

       If the variable command is executed inside a Tcl procedure, it creates
       local variables linked to the corresponding namespace variables (and
       therefore these variables are listed by info vars.)  In this way the
       variable command resembles the global command, although the global
       command resolves variable names with respect to the global namespace
       instead of the current namespace of the procedure.  If any values are
       given, they are used to modify the values of the associated namespace
       variables.  If a namespace variable does not exist, it is created and
       optionally initialized.

       A name argument cannot reference an element within an array.  Instead,
       name should reference the entire array, and the initialization value
       should be left off.  After the variable has been declared, elements
       within the array can be set using ordinary set or array commands.

EXAMPLES
       Create a variable in a namespace:

              namespace eval foo {
                  variable bar 12345
              }

       Create an array in a namespace:

              namespace eval someNS {
                  variable someAry
                  array set someAry {
                      someName  someValue
                      otherName otherValue
                  }
              }

       Access variables in namespaces from a procedure:

              namespace eval foo {
                  proc spong {} {
                      # Variable in this namespace
                      variable bar
                      puts "bar is $bar"

                      # Variable in another namespace
                      variable ::someNS::someAry
                      parray someAry
                  }
              }

SEE ALSO
       global(3tcl), namespace(3tcl), upvar(3tcl)

KEYWORDS
       global, namespace, procedure, variable



Tcl                                    8.0                        variable(3tcl)