Format Log Events as Text

Format Log Events as Text

Format Log Events as Text

Details

Format a LogEvent as human readable text using format.LogEvent(), which provides a quick and easy way to customize log messages. If you need more control and flexibility, consider using LayoutGlue instead.

see Fields

see Fields

see Fields

see Fields

Convert Layout to a character string Read a log file written using LayoutFormat

Format Tokens

This is the same list of format tokens as for format.LogEvent()

%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

%r

the raw log message (without string interpolation)

%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

See also

Other Layouts: Layout, LayoutGlue, LayoutJson

Super class

lgr::Layout -> LayoutFormat

Active bindings

fmt

a character scalar containing format tokens. See format.LogEvent().

timestamp_fmt

a character scalar. See base::format.POSIXct().

colors

a named list of functions (like the ones provided by the package crayon) passed on on format.LogEvent().

pad_levels

"right", "left" or NULL. See format.LogEvent().

Methods

Public methods

• LayoutFormat$new()

• LayoutFormat$format_event()

• LayoutFormat$set_fmt()

• LayoutFormat$set_timestamp_fmt()

• LayoutFormat$set_colors()

• LayoutFormat$set_pad_levels()

• LayoutFormat$toString()

• LayoutFormat$read()

• LayoutFormat$clone()

Inherited methods

• lgr::Layout$set_excluded_fields()

---

Method new()

Usage

LayoutFormat$new(
  fmt = "%L [%t] %m %j",
  timestamp_fmt = "%Y-%m-%d %H:%M:%OS3",
  colors = NULL,
  pad_levels = "right",
  excluded_fields = NULL
)

---

Method format_event()

Format a LogEvent

Usage

LayoutFormat$format_event(event)

Arguments

event

a LogEvent

---

Method set_fmt()

Usage

LayoutFormat$set_fmt(x)

---

Method set_timestamp_fmt()

Usage

LayoutFormat$set_timestamp_fmt(x)

---

Method set_colors()

Usage

LayoutFormat$set_colors(x)

---

Method set_pad_levels()

Usage

LayoutFormat$set_pad_levels(x)

---

Method toString()

Usage

LayoutFormat$toString()

---

Method read()

Usage

LayoutFormat$read(file, threshold = NA_integer_, n = 20L)

Arguments

threshold

a character or integer threshold

n

number of log entries to display

---

Method clone()

The objects of this class are cloneable with this method.

Usage

LayoutFormat$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Examples

# setup a dummy LogEvent
event <- LogEvent$new(
  logger = Logger$new("dummy logger"),
  level = 200,
  timestamp = Sys.time(),
  caller = NA_character_,
  msg = "a test message"
)
lo <- LayoutFormat$new()
lo$format_event(event)
#> [1] "ERROR [2025-07-23 06:40:29.119] a test message"