# 18.2.346. MPI_T_category_get_categories

MPI_T_category_get_categories — Query which categories are in a category

## 18.2.346.1. SYNTAX

### 18.2.346.1.1. C Syntax

    #include <mpi.h>

    int MPI_T_category_get_categories(int cat_index, int len, int indices[])

## 18.2.346.2. INPUT PARAMETERS

- `cat_index`: Index of the category to be queried.

- `len`: The length of the indices array.

## 18.2.346.3. OUTPUT PARAMETERS

- `indices`: An integer array of size len, indicating category indices.

## 18.2.346.4. DESCRIPTION

MPI_T_category_get_categories can be used to query which other categories are in a category.

## 18.2.346.5. ERRORS

MPI_T_category_get_categories will fail if:

- `MPI_T_ERR_NOT_INITIALIZED`: The MPI Tools interface not initialized

- `MPI_T_ERR_INVALID_INDEX`: The category index is invalid