---
name: "VistaIOGetAttr"
section: "3"
platform: "linux"
package: "libvistaio-dev"
version: "1.2.19-3+b2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/VistaIOGetAttr"
---

# VistaIOGetAttr(3)

fetch an attribute's value

## NAME

VistaIOGetAttr, VistaIOGetAttrValue - fetch an attribute's value

## SYNOPSIS

```
VistaIOGetAttrResult VistaIOGetAttr (list, name, dict, repn, value)
VistaIOAttrList list;
VistaIOStringConst name;
VistaIODictEntry *dict;
VistaIORepnKind repn;
VistaIOPointer value;
```

**typedef enum { VistaIOAttrFound, VistaIOAttrMissing, VistaIOAttrBadValue } VistaIOGetAttrResult;**

**VistaIOBoolean VistaIOGetAttrValue (***posn***,** *dict***,** *repn***,** *value***)**

**VistaIOAttrListPosn \****posn***;** **VistaIODictEntry \****dict***;** **VistaIORepnKind** *repn***;** **VistaIOPointer** *value***;**

## ARGUMENTS

- *list*

  **Specifies the list of attributes to be searched by name for the desired** **attribute.**

- *name*

  **Specifies the name of the desired attribute.**

- *posn*

  **Specifies the position of the desired attribute within its attribute list.**

- *dict*

  **May specify a dictionary to be used in recognizing a keyword** **stored as the attribute's value, or it may be** **NULL**

- *repn*

  **Specifies the representation in which the attribute value is to be**  **returned.**

- *value*

  **Specifies a location at which the attribute value is be returned.**

## DESCRIPTION

**These routines both return an attribute's value, but they differ in how the**  **attribute is identified:**

- •

  **VistaIOGetAttr fetches the value of the first attribute with the name**  *name* **in the list** *list***.**

- •

  **VistaIOGetAttrValue fetches the value of the attribute whose position**  **within an attribute list is** *posn***.**

**If a dictionary,** *dict***, has been provided and the attribute's value is**  **stored as a character string, the routine determines whether the string is**  **a keyword defined in the dictionary. If so, it uses the value associated**  **with that keyword rather than the attribute's original value. (See the**  **[VistaIOdictionary(3)](/VistaIOdictionary/3.md) manual page.)**

**The value obtained directly from the attribute, or indirectly via the**  **dictionary, is converted to the representation** *repn* **and then stored**  **at the location pointed to by** *value***. The** *repn* **argument may have**  **any VistaIORepnKind value (any of the values**  **returned by VistaIORegisterType(3). However, an attribute value that is a**  **string can only be returned as a string or a number, and other attribute**  **values can only be returned in the representation with which they are**  **stored. (The VistaIOGetAttrRepn(3) macro can be used to determine an**  **attribute value's representation.)**

**If** *repn* **calls for a number to be returned, the caller receives a copy**  **of the value stored with the attribute. If, on the other hand, it calls for**  **a string, attribute list, pointer, image, edge set, etc. to be returned,**  **the caller receives a pointer to the same value as that stored with the**  **attribute.**

## RETURN VALUES

**If the specified attribute is not found, VistaIOGetAttr returns** **VistaIOAttrMissing. If it is found but its value cannot be converted to the** **desired representation, VistaIOGetAttr returns VistaIOAttrBadValue.** **Otherwise, VistaIOGetAttr is successful and it returns VistaIOAttrFound,** **having stored the attribute's value at \****value***.**

**VistaIOGetAttrValue returns** **TRUE** **if it is successfully returning the attribute's value at \****value***, and** **FALSE** **if the value cannot be converted to the desired representation.**

## EXAMPLES

**The following code fragment prints the name of an image:**

```
VistaIOImage image;
VistaIOStringConst name;
```

**if (VistaIOGetAttr (VistaIOImageAttrList (image), VistaIONameAttr, NULL,**

**VistaIOStringRepn, (VistaIOPointer) & name) == VistaIOAttrFound)** **printf ("Name: %s\\n", name);**

## SEE ALSO

[**VistaIOExtractAttr**(3)](/VistaIOExtractAttr/3.md), [**VistaIOSetAttr**(3)](/VistaIOSetAttr/3.md), **VistaIOSetAttrValue**(3),\
 [**VistaIOattribute**(3)](/VistaIOattribute/3.md), [**VistaIOdictionary**(3)](/VistaIOdictionary/3.md),

## NOTES

**VistaIOGetAttr is meant for use with attribute lists representing sets, in**  **which each attribute name occurs at most once. If** *list* **contains**  **multiple attributes named** *name***, only the first is located and**  **returned.**

**The** *value* **argument must point to sufficient storage to contain a**  **value of the representation requested. Neither the routine nor the C**  **compiler can automatically check that this is so.**

## AUTHOR

**Art Pope \<pope@cs.ubc.ca\>**

**Adaption to vistaio: Gert Wollny \<gw.fossdev@gmail.com\>**