variable(3tcl)

NAME

   variable - create and initialize a namespace variable

SYNOPSIS

   variable ?name value...? 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 only links to variables in the global namespace.  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

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