# 18.2.347. MPI_T_category_get_cvars

MPI_T_category_get_cvars — Query which control variables are in a category

## 18.2.347.1. SYNTAX

### 18.2.347.1.1. C Syntax

    #include <mpi.h>

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

## 18.2.347.2. INPUT PARAMETERS

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

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

## 18.2.347.3. OUTPUT PARAMETERS

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

## 18.2.347.4. DESCRIPTION

MPI_T_category_get_cvars can be used to query which control variables are contained in a particular category.

## 18.2.347.5. ERRORS

MPI_T_category_get_cvars will fail if:

- `MPI_T_ERR_NOT_INITIALIZED`: The MPI Tools interface not initialized

- `MPI_T_ERR_INVALID_INDEX`: The category index is invalid