Multi argument open and STDERR

[Paul Weaver]

Thanks, that did the job very nicely, and exists as a package in ubuntu, which makes it far easier than converting a cpan one.

ffmpeg does tend to be very vague with documentation, we actually use a fork called ffmbc, but same principle.

ffprobe can do things in a more structured way, but I do like ffmpeg, as if it detects the duration, I know I'll be able to convert it, and the code already ran it so there was no need to do anything further down in the unreadable mess my code tends to land in.


________________________________________
From: london.pm-bounces at london.pm.org [london.pm-bounces at london.pm.org] on behalf of Dave Hodgkinson [davehodg at gmail.com]
Sent: 03 October 2013 22:34
To: London.pm Perl M[ou]ngers
Subject: Re: Multi argument open and STDERR

Capture::Tiny just did the job for me today. Screw line noise.

Sent from my iPhone

> On 3 Oct 2013, at 21:26, Paul Weaver <paul.weaver at bbc.co.uk> wrote:
>
> I have a program that needs to run an external program (ffmpeg)
>
> I do this by running
>
> my $cmd = "$FFMPEG -i '$file' 2>&1|"
> open(CMD, $cmd); while (<CMD>) { #blah } ; close(CMD);
>
> This works fine. Until there's a single quote in the filename.
>
> Reading the docs,
> open FILEHANDLE,MODE,EXPR,LIST
>
> Should do the trick, and if I do
>        open(CMD, "-|", "ls", "-l", $file);
>        while (<CMD>) {
>                print "   TEST: $_\n";
>        }
>        close(CMD);
>
> It works fine.
>
> The trouble is, ffmpeg outputs the -i information on STDERR, not STDOUT.
>
>        open(CMD, "-|", "ffmpeg", "-i", $file, "2>&1");
>        while (<CMD>) {
>                print "   TEST: $_\n";
>        }
>        close(CMD);
>
> Obviously doesn't work, as 2>&1 is a bash redirection.
>
> How can I capture STDERR?
>
> Thanks
>
>
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