Log Messages to Console and File with Optional JSON Format

A utility function for logging messages to the console or (optionally) to a log file. Messages can be stored as plain text (default) or in JSON format.

Usage

logr_msg(message, level = "INFO", log_file = NULL, json = FALSE)

Arguments

message

A character string representing the message to be logged.

level

A character string indicating the log level. One of:

• "FATAL"

• "ERROR"

• "WARN"

• "SUCCESS"

• "INFO" (default)

• "DEBUG"

• "TRACE"

log_file

A character string specifying the path to the log file. If NULL, logs are not saved to a file, and only console logging is performed. Defaults to NULL.

json

A logical value indicating whether to save logs in JSON format. Defaults to FALSE. When TRUE, logs are written to the specified log_file as JSON objects.

Value

The function is called for its side effects of logging messages and does not return a value.

Details

• Console Logging: All messages are always logged to the console.

• File Logging: If log_file is specified, messages are logged to the file in either plain text or JSON format, depending on the value of json.

• JSON Logs: When json = TRUE, log messages are stored as structured JSON objects with the fields:

  • timestamp: The time the message was logged.

  • level: The severity level of the log.

  • message: The actual log message.

Note

logr_msg() uses the logger package for console and plain text logging and integrates JSON logging using the jsonlite package.

See also

• logger::log_appender() for configuring log destinations.

• logger::log_formatter() for customizing log message formats.

• jsonlite::toJSON() for converting R objects to JSON.

Examples

# log a simple informational message to the console
logr_msg("Application started.")
#> INFO [2025-07-24 06:20:15] Application started.

# log an error message to the console and a file in plain text format
logr_msg(
  message = "Failed to connect to the database.",
  level = "ERROR",
  log_file = "error_log.txt"
)
#> ERROR [2025-07-24 06:20:15] Failed to connect to the database.

# log a success message in JSON format
logr_msg(
  message = "User login successful.",
  level = "SUCCESS",
  log_file = "app_log.json",
  json = TRUE
)
#> SUCCESS [2025-07-24 06:20:15] User login successful.

# log a warning message to the console only
logr_msg(
  message = "Low memory warning.",
  level = "WARN"
)
#> {"time":"2025-07-24 06:20:15","level":"WARN","ns":"ttdviewer","ans":"global","topenv":"ttdviewer","fn":"logr_msg","node":"pkrvmpptgkbjq6m","arch":"x86_64","os_name":"Linux","os_release":"6.11.0-1018-azure","os_version":"#18~24.04.1-Ubuntu SMP Sat Jun 28 04:46:03 UTC 2025","pid":8263,"user":"runner","msg":"Low memory warning."}