Print or Format Logging Data

Print or Format Logging Data

Usage

# S3 method for class 'LogEvent'
print(
  x,
  fmt = "%L [%t] %m  %f",
  timestamp_fmt = "%Y-%m-%d %H:%M:%S",
  colors = getOption("lgr.colors"),
  log_levels = getOption("lgr.log_levels"),
  pad_levels = "right",
  ...
)

# S3 method for class 'LogEvent'
format(
  x,
  fmt = "%L [%t] %m  %f",
  timestamp_fmt = "%Y-%m-%d %H:%M:%S",
  colors = NULL,
  log_levels = getOption("lgr.log_levels"),
  pad_levels = "right",
  ...
)

Arguments

x

a LogEvent

fmt

A character scalar that may contain any of the tokens listed bellow in the section Format Tokens.

timestamp_fmt

see format.POSIXct()

colors

A list of functions that will be used to color the log levels (likely from crayon::crayon).

log_levels

named integer vector of valid log levels

pad_levels

right, left or NULL. Whether or not to pad the log level names to the same width on the left or right side, or not at all.

...

ignored

Value

x for print() and a character scalar for format()

Format Tokens

%t

The timestamp of the message, formatted according to timestamp_fmt)

%l

the log level, lowercase character representation

%L

the log level, uppercase character representation

%k

the log level, first letter of lowercase character representation

%K

the log level, first letter of uppercase character representation

%n

the log level, integer representation

%g

the name of the logger

%p

the PID (process ID). Useful when logging code that uses multiple threads.

%c

the calling function

%m

the log message

%f

all custom fields of x in a pseudo-JSON like format that is optimized for human readability and console output

%j

all custom fields of x in proper JSON. This requires that you have jsonlite installed and does not support colors as opposed to %f

Examples

# standard fields can be printed using special tokens
x <- LogEvent$new(
  level = 300, msg = "a test event", caller = "testfun()", logger = lgr
)
print(x)
#> WARN  [2025-04-14 20:58:51] a test event
print(x, fmt = c("%t (%p) %c: %n - %m"))
#> 2025-04-14 20:58:51 (7042) testfun(): 300 - a test event
print(x, colors = NULL)
#> WARN  [2025-04-14 20:58:51] a test event

# custom values
y <- LogEvent$new(
  level = 300, msg = "a gps track", logger = lgr,
  waypoints = 10, location = "Austria"
)

# default output with %f
print(y)
#> WARN  [2025-04-14 20:58:51] a gps track  {waypoints: `10`, location: `Austria`}

# proper JSON output with %j
if (requireNamespace("jsonlite")){
print(y, fmt = "%L [%t] %m  %j")
}
#> WARN  [2025-04-14 20:58:51] a gps track  {"waypoints":10,"location":"Austria"}