class Logger


The Logger class provides a simple but sophisticated logging utility that you can use to output messages.

The messages have associated levels, such as INFO or ERROR that indicate their importance. You can then give the Logger a level, and only messages at that level of higher will be printed.

For instance, in a production system, you may have your Logger set to INFO or even WARN. When you are developing the system, however, you probably want to know about the program’s internal state, and would set the Logger to DEBUG.


require "logger"

log =
log.level = Logger::WARN

log.debug("Created logger")"Program started")
log.warn("Nothing to do!")

  File.each_line(path) do |line|
    unless line =~ /^(\w+) = (.*)$/
      log.error("Line in wrong format: #{line}")
rescue err
  log.fatal("Caught exception; exiting")

Defined in:

Constant Summary

DEBUG = Severity::DEBUG
ERROR = Severity::ERROR
FATAL = Severity::FATAL
INFO = Severity::INFO
WARN = Severity::WARN

Class Method Summary

Instance Method Summary

Instance methods inherited from class Reference

==(other : self)
, hash hash, inspect(io : IO) : Nil inspect, object_id : UInt64 object_id, same?(other : Reference)
same?(other : Nil)
, to_s(io : IO) : Nil to_s

Instance methods inherited from class Object

!=(other) !=, !~(other) !~, ==(other) ==, ===(other)
===(other : YAML::Any)
===(other : JSON::Any)
, =~(other) =~, class class, clone clone, crystal_type_id crystal_type_id, dup dup, hash hash, inspect
inspect(io : IO)
, itself itself, not_nil! not_nil!, tap(&block) tap, to_json to_json, to_pretty_json(io : IO)
, to_s
to_s(io : IO)
, to_yaml(io : IO)
, try(&block) try

Class methods inherited from class Object

==(other : Class) ==, ===(other) ===, cast(other) : self cast, from_json(string_or_io) : self from_json, from_yaml(string : String) : self from_yaml, hash hash, inspect(io) inspect, name : String name, to_s(io) to_s, |(other : U.class) |

Class Method Detail

def : IO) #

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Instance Method Detail

def close #

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def debug(message, progname = nil) #

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def debug(progname = nil, &block) #

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def debug? #

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def error(message, progname = nil) #

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def error(progname = nil, &block) #

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def error? #

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def fatal(progname = nil, &block) #

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def fatal(message, progname = nil) #

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def fatal? #

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def formatter : String, Time, String, String, IO -> #

def formatter=(formatter) #

def info(progname = nil, &block) #

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def info(message, progname = nil) #

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def info? #

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def level : Logger::Severity #

def level=(level : Severity) #

def log(severity, message, progname = nil) #

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def log(severity, progname = nil, &block) #

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def progname : String #

def progname=(progname : String) #

def unknown(message, progname = nil) #

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def unknown(progname = nil, &block) #

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def unknown? #

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def warn(progname = nil, &block) #

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def warn(message, progname = nil) #

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def warn? #

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