Shell.PerfLog.define_statistic

### Method

# Shell PerfLogdefine_statistic

#### Declaration [src]

    void
    shell_perf_log_define_statistic (
      ShellPerfLog* perf_log,
      const char* name,
      const char* description,
      const char* signature
    )

#### Description [src]

Defines a statistic. A statistic is a numeric value that is stored by the performance log and recorded periodically or when `shell_perf_log_collect_statistics()` is called explicitly.

Code that defines a statistic should update it by calling the update function for the particular data type of the statistic, such as shell_perf_log_update_statistic_i(). This can be done at any time, but would normally done inside a function registered with shell_perf_log_add_statistics_callback(). These functions are called immediately before statistics are recorded.

#### Parameters

`name`

  Type: `const char*`

  Name of the statistic and of the corresponding event. This should follow the same guidelines as for shell_perf_log_define_event().

  The data is owned by the caller of the method.
  The value is a NUL terminated UTF-8 string.

`description`

  Type: `const char*`

  Human readable description of the statistic.

  The data is owned by the caller of the method.
  The value is a NUL terminated UTF-8 string.

`signature`

  Type: `const char*`

  The type of the data stored for statistic. Must currently be ‘i’ or ‘x’.

  The data is owned by the caller of the method.
  The value is a NUL terminated UTF-8 string.