The logging package uses a formatter that behaves differently when the input is a string or other R object. If the first argument is a string, then sprintf is being called -- otherwise it does something like log_eval and logs the R expression(s) and the result(s) as well.

  .logcall =,
  .topcall =,
  .topenv = parent.frame()



string and further params passed to sprintf or R expressions to be evaluated


the logging call being evaluated (useful in formatters and layouts when you want to have access to the raw, unevaluated R expression)


R expression from which the logging function was called (useful in formatters and layouts to extract the calling function's name or arguments)


original frame of the .topcall calling function where the formatter function will be evaluated and that is used to look up the namespace as well via logger:::top_env_name


character vector

See also

This is a log_formatter, for alternatives, see formatter_paste, formatter_glue, formatter_glue_or_sprintf, formatter_json, formatter_pander and skip_formatter for marking a string not to apply the formatter on it.


if (FALSE) {
log_info('foo %s', 'bar')
log_info('vector %s', 1:3)
log_info(12, 1+1, 2 * 2)