From: "yermej@..." <yermej@...>
Date: 2007-10-27T05:45:02+09:00
Subject: Re: cant seem to get system() & pipe to work together

On Oct 25, 3:58 pm, "dtow...@gmail.com" <dtow...@gmail.com> wrote:
> I am trying to run a command line utility which converts a wma file to
> a mp3 (i want to be able to do this for batch files) using FFMpeg &
> LAME. I am trying to run the following command from ruby:
>
> "C:\Documents and Settings\dt\Desktop\my stuff\songs\wma\ffmpeg.exe" -
> i "C:\Documents and Settings\dt\Desktop\my stuff\songs\Who The
> \Quadrophenia\07-0 - Who The - Love Reign O'er Me.wma" -vn -f wav - |
> "C:\Documents and Settings\dt\Desktop\my stuff\songs\wma\lame.exe" -V
> 6 - "C:\Documents and Settings\dt\Desktop\my stuff\songs\\Who The
> \Quadrophenia\07-0 - Who The - Love Reign O'er Me.mp3"
>
> It works perfect from the command line, but no matter how i try it
> (with double quotes, single quotes, backticks, etc) it doesnt seem to
> want to work from ruby
>
> Here is an example of the code I have
>
>  ffmpeg = '"C:\\Documents and Settings\\dt\\Desktop\\my stuff\\songs\
> \wma\\ffmpeg.exe"'
>   lame = '"C:\\Documents and Settings\\dt\\Desktop\\my stuff\\songs\
> \wma\\lame.exe"'
>
> newFile = child.sub('wma', 'mp3')
> #cmd = ffmpeg + " -i " + child + " -vn -f wav - | "  + lame + " -V 6 -
> " + newFile
> cmd1 = "#{ffmpeg} -i #{child} -vn -f wav - | #{lame} -V 6 -
> #{newFile}"
> puts cmd1
> system(cmd1)
>
> NOTE: child points to the same file wma file as above.
>
> If i copy and paste the output of the puts command above into a
> command window, it works fine...but from ruby, it seems to ignore the
> pipe (|) command. I dont know if this is a windows issue, or if i am
> missing something obvious. Any help is greatly appreciated.

As far as I can tell, this is due to the way the Windows command
interpreter handles double-quotes when a pipe is present along with
the way Ruby's #system method calls the interpreter.

>From a few tests I did, it seemed the leading double-quote was being
stripped from the command line, but adding another did not fix the
problem. I think you could fix it by either relocating your
executables to a path with no spaces or using a temp file rather than
a pipe. Maybe not optimal, but, like you, I fiddled with all sorts of
single/double quotes and escaping and it didn't like any of it.