# u91 user exit

The u0091 user exit reads and writes
D3 shell variables.

## Syntax

```
oconv("", ’u0091’)
oconv("var.name", "u0091")
oconv("var.name^var.value", "u0091")
oconv("var.name]", "u0091")
```

## Description

- The first form returns a list of all active user shell variables (not including their values).

- The second form returns the value of a specific variable.

- The third form sets the value of a specific variable. Note that unlike the retrieval forms, the user should avoid the @$ prefix before the variable name. The ^ symbol indicates an attribute mark.

- The fourth form deletes a shell variable. As with the third form, the user should avoid the @$ prefix before the variable name. The ] symbol indicates a value mark.

This user exit is used by the TCL set, unset, and penv commands.

## See also

- [@ shell variable](https://d3codex.com/tcl/shell-variable/)
- [penv command](https://d3codex.com/tcl/penv-command/)
- [set command](https://d3codex.com/tcl/set-command/)
- [unset command](https://d3codex.com/tcl/unset-command/)

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Source: https://d3codex.com/pickbasic-flashbasic/u91-user-exit/ - part of the D3Codex reference.