log4r

log4r

Simple, fast logging for R.

Basic Usage

library(log4r)

# Create logger
logger <- logger()

# Log messages
debug(logger, "Debug message")
info(logger, "Info message")
warn(logger, "Warning message")
error(logger, "Error message")
fatal(logger, "Fatal message")

Logger Configuration

# Create logger with options
logger <- logger(
  threshold = "INFO",
  appenders = console_appender()
)

# With file appender
logger <- logger(
  threshold = "DEBUG",
  appenders = file_appender("app.log")
)

# Multiple appenders
logger <- logger(
  threshold = "INFO",
  appenders = list(
    console_appender(),
    file_appender("app.log")
  )
)

Log Levels

# Levels (lowest to highest)
# DEBUG < INFO < WARN < ERROR < FATAL

# Set threshold
logger <- logger(threshold = "WARN")

# Level constants
log4r:::DEBUG
log4r:::INFO
log4r:::WARN
log4r:::ERROR
log4r:::FATAL

Appenders

# Console appender
console_appender(layout = default_log_layout())

# File appender
file_appender(
  file = "app.log",
  append = TRUE,
  layout = default_log_layout()
)

# Custom appender
my_appender <- function(level, ...) {
  msg <- paste(..., collapse = " ")
  # Custom logic
  cat(sprintf("[%s] %s\n", level, msg))
}

Layouts

# Default layout
default_log_layout()

# Custom layout function
my_layout <- function(level, ...) {
  msg <- paste(..., collapse = " ")
  sprintf("[%s] [%s] %s",
          format(Sys.time(), "%Y-%m-%d %H:%M:%S"),
          level,
          msg)
}

logger <- logger(
  appenders = console_appender(layout = my_layout)
)

Formatted Messages

# Use sprintf-style formatting
info(logger, sprintf("Processing file: %s", filename))
info(logger, sprintf("Completed %d of %d", current, total))

# Or paste
info(logger, "User", user, "logged in")

Conditional Logging

# Check level before expensive operations
if (logger$threshold <= log4r:::DEBUG) {
  debug(logger, expensive_computation())
}

Global Logger

# Create global logger
.logger <- logger(threshold = "INFO")

# Wrapper functions
log_debug <- function(...) debug(.logger, ...)
log_info <- function(...) info(.logger, ...)
log_warn <- function(...) warn(.logger, ...)
log_error <- function(...) error(.logger, ...)

# Use throughout application
log_info("Application started")