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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?

On Tue, Feb 3, 2009 at 11:19 AM, Daniel Vartanov
<> wrote:
> 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

Thank you very much, great idea! I missed in my mind, that puts just
uses global variable $stdout.