Some legacy code produces output to STDOUT during execution. I need to
capture it on even-based model, something like the following:
capture the_legacy_code_lambda do |content|
# do something with content each time something appears in STDOUT
end
how can I manage this? Are there any idioms?
You can reassign to the global $stdout object any object which
provides the method #write. You could use that to capture the output
something like this:
class Capture
def initialize(*args, &block)
@block = block
end
def write(txt)
@block.call(txt)
end
end
def capture(code, &block)
old_stdout = $stdout
begin
$stdout = Capture.new(&block)
code.call
ensure
$stdout = old_stdout
end
end
def legacy_code
puts "hello world"
puts "me again"
raise Exception, "Oh no!"
end
puts "start"
begin
capture(proc { legacy_code }) do |txt|
STDOUT.print "captured ["
STDOUT.print txt
STDOUT.puts "]"
STDOUT.flush
end
rescue Object => e
puts "Got exception"
raise
end
puts "end"
# $ ruby capture-stdout.rb
# start
# captured [hello world]
# captured [
# ]
# captured [me again]
# captured [
# ]
# Got exception
# capture-stdout.rb:23:in `legacy_code': Oh no! (Exception)
# etc.
Regards,
Sean
