# 18.2.352. MPI_T_cvar_get_num

MPI_T_cvar_get_num — Query the number of control variables

## 18.2.352.1. SYNTAX

### 18.2.352.1.1. C Syntax

    #include <mpi.h>

    int MPI_T_cvar_get_num(int *num_cvar)

## 18.2.352.2. OUTPUT PARAMETERS

- `num_cvar`: Current number of control variables.

## 18.2.352.3. DESCRIPTION

MPI_T_cvar_get_num can be used to query the current number of control variables. The number of control variables may increase throughout the execution of the process but will never decrease.

## 18.2.352.4. ERRORS

MPI_T_cvar_get_num will fail if:

- `MPI_T_ERR_NOT_INITIALIZED`: The MPI Tools interface not initialized