---
name: "BackgdErr"
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/BackgdErr/3tcl"
---

# BackgdErr(3tcl)

report Tcl error that occurred in background processing

```

```

## NAME

Tcl\_BackgroundError - report Tcl error that occurred in background processing

## SYNOPSIS

```
#include <tcl.h>

Tcl_BackgroundError(interp)
```

## ARGUMENTS

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

  Interpreter in which the error occurred.

  ```

  ```

## DESCRIPTION

This procedure is typically invoked when a Tcl error occurs during \`\`background processing'' such as executing an event handler. When such an error occurs, the error condition is reported to Tcl or to a widget or some other C code, and there is not usually any obvious way for that code to report the error to the user. In these cases the code calls **Tcl\_BackgroundError** with an *interp* argument identifying the interpreter in which the error occurred.  At the time **Tcl\_BackgroundError** is invoked, the interpreter's result is expected to contain an error message. **Tcl\_BackgroundError** will invoke the **bgerror** Tcl command to report the error in an application-specific fashion. If no **bgerror** command exists, or if it returns with an error condition, then **Tcl\_BackgroundError** reports the error itself by printing a message on the standard error file.

**Tcl\_BackgroundError** does not invoke **bgerror** immediately because this could potentially interfere with scripts that are in process at the time the error occurred. Instead, it invokes **bgerror** later as an idle callback. **Tcl\_BackgroundError** saves the values of the **errorInfo** and **errorCode** variables and restores these values just before invoking **bgerror**.

It is possible for many background errors to accumulate before **bgerror** is invoked.  When this happens, each of the errors is processed in order.  However, if **bgerror** returns a break exception, then all remaining error reports for the interpreter are skipped.

## KEYWORDS

background, bgerror, error