On Sun, Jul 9, 2017, 19:37 Mike Martin wrote:
> Hi
> I am trying to use Open3 to capture stderr and avoiding the shell ie:
> my $str="-v 35 -i /data/Downloads/testinput.mp4 -c:v libx264 -preset fast
> -crf 28 -g 25 -c:a libmp3lame -b:a 128000 -threads 4 -af volume=2.5 -vf
> scale='352:trunc(ow/((1/sar)*dar)/2)*2',fps='fps= 20',setsar='1/1'
> -profile:a aac_he_v2 -strict -2 -y /home/mike/testopen.mp4";
> use Text::ParseWords;
> @args = quotewords('\s+', "'", $str);
>
> use IPC::Open3;
>
> local(*HIS_IN, *HIS_OUT, *ERR);
> my $cmd='ffmpeg';
> my $pid=open3(undef, undef, *ERR,$cmd, @args) or die print "$!";
> my $line;
>
> while (sysread ERR, $line, 256){
> print $line;
> }
> waitpid($pid, 0);
>
> However the output is buffered for around 2 minutes at a time rather
> immediately being printed
>
> Is there any way around this
>
Are you certain the buffering is in the read from ERR and not in the print?
STDERR is not supposed to be buffered. Try adding
$| = 1;
Near the top of your program. That will turn off any buffering of the Perl
5 script's STDOUT.
By default, Perl 5 will buffer STDOUT if it isn't writing to a
pseudoterminal (eg if you are piping the output of the Perl 5 script to
something else like tee.)
