- Pipe calls to $stdout and $stderr to a file
- Pipe calls to $stdout and $stderr to an instance of Ruby's logger class
- Pipe calls to an instance of Ruby's logger class to $stdout
I wrote this gem for three reasons:
- Have Ruby's logger library output to STDOUT/STDERR in addition to a file
- Have the
putsstatements of external libraries go through my custom logger class - Tee STDOUT/STDERR to a file
In general, I consider redirecting Ruby's STDOUT and STDERR from within the program to be a last resort, because another person using your program might not expect this special behavior.
Most of the time it is possible to use standard Unix tools to accomplish the same task without having to change your program. Here are a few examples:
$: ruby myscript.rb > my_file.log
$: ruby myscript.rb | tee myfile.log
In particular, I consider it good practise to use the operating system's logging facilities (see man logger).
This allows to change the logging behaviour without changing the actual program:
$: ruby myscript.rb | logger
If you want to have logs on the console as well:
$: ruby myscript.rb | tee /dev/null | logger
This only works for $stdout and $stderr and not for STDOUT and STDERR, since they are constants
that should not be reassigned/redefined.
$: gem install teerb
# Tee $stdout and $stderr to several files
log_file = File.open("debug.log", "a")
tee = TeeRb::Tee.new(log_file)
tee.enable
puts 'puts hello'
$stdout.puts 'stdout hello'
$stderr.puts 'stderr hello'
tee.disable
puts 'puts hello'
$stdout.puts 'stdout hello'
$stderr.puts 'stderr hello'
# same as above but with block syntax
log_file = File.open("debug.log", "a")
TeeRb::Tee.new(log_file) do
puts 'puts hello'
$stdout.puts 'stdout hello'
$stderr.puts 'stderr hello'
end
# Capture $stdout and $stderr and send it through `logger`
require 'logger'
log_file = File.open("debug.log", "a")
logger = Logger.new(log_file)
tee = TeeRb::LoggerTee.new(logger)
tee.enable
logger.warn "hello"
$stderr.puts "stderr hello"
puts "stdout hello"
# Pipe calls to an instance of Ruby's logger class to $stdout
require 'logger'
log_file = File.open("debug.log", "a")
logger = Logger.new(TeeRb::IODelegate.new(log_file, STDOUT))
logger.warn "warn"
$stderr.puts "stderr hello"
puts "stdout hello"
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