Detailed Description

The Regex operator searches substrings from input value using regular expression search pattern.

The Regex operator has the following properties:

Arguments

The Regex search pattern is a string that describes the expected input, with special character entities that indicate blocks (groups) that will be copied to output argument values (in the order of occurrence).

Let's assume that an input string like this:

Temperature: 25.1 C; Humidity: 55 %

A Regex operator with the following Pattern can output values to temperature and humidity arguments:

Pattern="Temperature: (\S+) C;\s+Humidity: (\S+) %"

Regex search patterns can detect and copy values from very complex input strings.

Below is a table with the most useful special characters in patterns:

You can learn more about regex possibilities, at:

• Boost regex page
• Wikipedia regex page

Actual Processing Code of the Evaluate

unsigned int Regex::Process()
{
  m_output = m_input;

  if (static_cast<string>(m_input) != m->cachedInput)
  {
    m->cachedInput = static_cast<string>(m_input);
    if (!m->cachedInput.empty() && m->regexOK)
    {
      boost::smatch matches;
      if (boost::regex_search(m->cachedInput, matches, m->regex))
      {
        size_t index{1};
        for (auto arg : m_arguments)
        {
          auto s = static_cast<std::string>(matches[index]);
          if (index < matches.size())
            *arg = s;
          else
            arg->SetValue(""); // clear all non-matcing arguments
          ++index;
        }
      }
      else
      {
        GetParent()->ReportConfigurationFault(this, "Input '" + m->cachedInput +
                                              "' does not match the configured regex pattern '" +
                                              m->pattern + "'");
        for (auto arg : m_arguments)
          arg->SetValue(""); // clear all arguments on pattern mismatch
        m->faultReported = true;
        return STATUS_SIGNAL_FAULT;
      }
    }
    else
      for (auto arg : m_arguments)
        arg->SetValue("");

    if (m->regexOK && m->faultReported)
    {
      GetParent()->ClearConfigurationFault(this);
      m->faultReported = false;
    }
  }
  return STATUS_OK;
}