Examples StructuredOutput

StructuredOutput example

StructuredOutput

This example shows how to switch logme output between plain text, JSON and XML at runtime. It also demonstrates structured field name customization.

What it demonstrates

• Keeping the default text formatter unchanged.
• Switching OutputFlags::Format to JSON.
• Switching OutputFlags::Format to XML.
• Renaming structured fields with SetOutputFieldName().
• Restoring default field names with ResetOutputFieldNames().

Notes

JSON output is emitted as one JSON object per log record. XML output is emitted as one <event> element per log record.

Use logmefmt --finalize when the stream must be converted into a complete JSON or XML document.

Console output

2026-06-10 14:51:46:381   PrintMessage(): text format
{"timestamp":"2026-06-10 14:51:46:381","level":"info","channel":"","method":"PrintMessage","message":"json format"}
{"timestamp":"2026-06-10 14:51:46:381","lvl":"info","channel":"","method":"PrintMessage","msg":"json with custom field names"}
<event><timestamp>2026-06-10 14:51:46:381</timestamp><level>info</level><channel></channel><method>PrintMessage</method><message>xml format</message></event>
2026-06-10 14:51:46:381   {} PrintMessage(): text format again

Source code

Sources

Repository folder: examples/StructuredOutput

StructuredOutput.cpp

Open in repository

#include <Logme/Logme.h>

static void PrintMessage(const char* text)
{
  LogmeI("%s", text);
}

int main()
{
  Logme::OutputFlags flags = Logme::Instance->GetDefaultChannelPtr()->GetFlags();

  PrintMessage("text format");

  flags.Format = Logme::OUTPUT_JSON;
  flags.Channel = true;
  flags.Method = true;
  Logme::Instance->GetDefaultChannelPtr()->SetFlags(flags);
  PrintMessage("json format");

  Logme::SetOutputFieldName(Logme::OUTPUT_FIELD_MESSAGE, "msg");
  Logme::SetOutputFieldName(Logme::OUTPUT_FIELD_LEVEL, "lvl");
  PrintMessage("json with custom field names");

  Logme::ResetOutputFieldNames();
  flags.Format = Logme::OUTPUT_XML;
  Logme::Instance->GetDefaultChannelPtr()->SetFlags(flags);
  PrintMessage("xml format");

  flags.Format = Logme::OUTPUT_TEXT;
  Logme::Instance->GetDefaultChannelPtr()->SetFlags(flags);
  PrintMessage("text format again");

  return 0;
}

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