From: Ed Hames <ehames@...>
Date: 2008-05-07T05:20:06+09:00
Subject: Re: Logging stdout/stderr/stdin of an spawn process (Open4::spawn)

On Apr 29, 12:05 pm, Edgardo Hames <eha...@gmail.com> wrote:
>
> I need to log all the input (typed by the user) and the stdout/stderr
> of a process. The #script method below should behave pretty much like
> the Unix script application. This way, my application can issue
> several commands, show their output to the user an let them whatever
> is needed.
>
> def script cmd, log
>         # prepare $stdin to save its content into log
>         # prepare $stdout to save its content into log
>         # prepare $stderr to save its content into log
>         status = Open4::spawn cmd, 'stdin' => $stdin, 'stdout' =>
> $stdout, 'stderr' => $stderr
> end

I finally managed to do it. Open4::spawn allows any object to be used
as stdin/stdout/stderr as long as they support 'each', 'read', or
'to_s' or '<<'. So I just created a wrapper class that encapsulates
two descriptors logging al I/O operations.

Best regards,
Edgardo


# BEGIN SCRIPT
require 'rubygems'
require 'open4'

class LoggingIO
        def initialize io, log
                @io = io
                @log = log
        end

        def gets(sep_string=$/)
                res = @io.gets(sep_string)
                log res
                res
        end

        def << obj
                res = @io << obj
                log obj
                res
        end

        def log obj
                str = obj ? obj.to_s : "(nil)\n"
                @log << str
        end
        private :log
end

def execute cmd, logfile = nil
        log = nil
        stdin = $stdin
        stdout = $stdout
        stderr = $stderr

        if (logfile)
                log = File.open(logfile, 'a+')
                stdin  = LoggingIO.new($stdin, log)
                stdout = LoggingIO.new($stdout, log)
                stderr = LoggingIO.new($stderr, log)
        end

        status = Open4::spawn cmd, 'stdin' => stdin, 'stdout' =>
stdout, 'stderr' => stderr
        log.close if log
        status
end
# END SCRIPT