---
name: "UpVar"
section: "3tcl"
platform: "linux"
package: "tcl8.3-doc"
version: "8.3.5-13"
release: "Debian 5.0 (Lenny)"
platforms: ["linux"]
url: "https://new.carta.tech/UpVar/3tcl"
---

# UpVar(3tcl)

link one variable to another

```

```

## NAME

Tcl\_UpVar, Tcl\_UpVar2 - link one variable to another

## SYNOPSIS

```
#include <tcl.h>

int
Tcl_UpVar(interp, frameName, sourceName, destName, flags)

int
Tcl_UpVar2(interp, frameName, name1, name2, destName, flags)
```

## ARGUMENTS

- Tcl\_Interp *\*interp* (in)

  Interpreter containing variables;  also used for error reporting.

- char *\*frameName* (in)

  Identifies the stack frame containing source variable. May have any of the forms accepted by the **upvar** command, such as **#0** or **1**.

- char *\*sourceName* (in)

  Name of source variable, in the frame given by *frameName*. May refer to a scalar variable or to an array variable with a parenthesized index.

- char *\*destName* (in)

  Name of destination variable, which is to be linked to source variable so that references to *destName* refer to the other variable.  Must not currently exist except as an upvar-ed variable.

- int *flags* (in)

  Either TCL\_GLOBAL\_ONLY or 0;  if non-zero, then *destName* is a global variable;  otherwise it is a local to the current procedure (or global if no procedure is active).

- char *\*name1* (in)

  First part of source variable's name (scalar name, or name of array without array index).

- char *\*name2* (in)

  If source variable is an element of an array, gives the index of the element. For scalar source variables, is NULL.

  ```

  ```

## DESCRIPTION

**Tcl\_UpVar** and **Tcl\_UpVar2** provide the same functionality as the **upvar** command:  they make a link from a source variable to a destination variable, so that references to the destination are passed transparently through to the source. The name of the source variable may be specified either as a single string such as **xyx** or **a(24)** (by calling **Tcl\_UpVar**) or in two parts where the array name has been separated from the element name (by calling **Tcl\_UpVar2**). The destination variable name is specified in a single string;  it may not be an array element.

Both procedures return either TCL\_OK or TCL\_ERROR, and they leave an error message in the interpreter's result if an error occurs.

As with the **upvar** command, the source variable need not exist; if it does exist, unsetting it later does not destroy the link.  The destination variable may exist at the time of the call, but if so it must exist as a linked variable.

## KEYWORDS

linked variable, upvar, variable