my $FIFO=undef;

mkfifo( $svitok_truby, 0700 ) || die 'Ошиб&#10
+82;а создания &
+#1090;рубы  '.$svitok_truby.'  : '.$!;
local $SIG{CHLD} = "IGNORE";

if( $nomer_vosproizvodyshchego_protsessu=fork ){

  $|=1;
  open( $FIFO, '>', $svitok_truby ) || die 'Не о&#10
+90;крыть труб&#
+1091; '.$svitok_truby.' на запи&#
+1089;ь : '.$!;

  <sniped>

  print $FIFO 'pause';

  <sniped>

}else{

  exec '/usr/bin/mplayer -slave -input file='.$svitok_truby.' /tmp/1.f
+lac';

}

close( $FIFO );
unlink $svitok_truby;
[download]

Just one question, is there a flush command -- to execute after each writing to pipe?

I did test more and have noticed weird connection between input in parent and pausing of mplayer, though to pipe was sent nothing at all -- parent just does its own work, w/o sending a thing to pipe, for example:

mkfifo( $svitok_truby, 0700 ) || die 'Ошиб&#10
+82;а создания &
+#1090;рубы  '.$svitok_truby.'  : '.$!;

# Управляющ&#107
+2;я часть ("род
+итель").
if( $nomer_vosproizvodyshchego_protsessu=fork ){

  $|=1;

  use Term::ReadKey;
  ReadMode 'cbreak';

  # Parent
  while( 1 ){

    $knopka=&ReadKey( 0 );

    if( $knopka eq '/' ){
      system( '/bin/date' );

    }elsif( $knopka eq $knopka_vyhodu ){
      system( '/bin/echo quit >'.$svitok_truby );
      last;
    }
  }

}else{
  ## Child
  for( $i=0; $i<=$#svitok_na_vosproizvedenie; $i++ ){
    system( '/usr/bin/mplayer -slave -input file='.$svitok_truby.' '.$
+svitok_na_vosproizvedenie_kom[$i] );
  }
}

ReadMode 'normal';
unlink $svitok_truby;
[download]

So, when i press key / -- parent just outputs date. But many times pressing, once, «mplayer2» will pause playing -- though nothing was sent to pipe! -- And that input-pipe relation i can not understand. Module «Term» does not have influence -- i had the same w/ the «read» function.

Oh! The site terribly corrupts my input!

Thanks for your answers.

Sorry, I neglected to set flush on the pipe, which is why you saw the issue. That can be accomplished by explicitly importing IO::Handle and calling autoflush. If I write a complete, self-contained script wrapping date, it might look like:

#!/usr/bin/perl
use strict;
use warnings;

use POSIX qw( mkfifo );
use IO::Handle;

my $svitok_truby = 'tmp.pp';
mkfifo( $svitok_truby, 0700 ) || die "Pipe fail;  $svitok_truby  : $!"
+;
local $SIG{CHLD} = "IGNORE";

my @args = ('perl','-MIO::Handle','-E',<<'EOC',$svitok_truby);
$| = 1;
open my $fh, "<", $ARGV[0];
while(read $fh, my($char), 1) {
    print $char;
}
EOC

my $pid = fork();
die "Fork failed\n" unless defined $pid;
if ($pid == 0) {
    exec @args;
}

open (my $FIFO, '>', $svitok_truby)  || die "can't open $svitok_truby:
+ $!";
$FIFO->autoflush(1);
while(read STDIN, my($char), 1) {
    print $FIFO $char;
}
close($FIFO);

END {
    unlink $svitok_truby;
}
[download]

To modify this from piping into the toy echo program, you would swap @args (including the here-doc, which runs until EOC) to whatever is appropriate for your program, probably (untested):

my @args = ('/usr/bin/mplayer', '-slave', '-input', "file=$svitok_trub
+y", $svitok_na_vosproizvedenie_kom[$i]);
[download]

It's possible you will still see buffering issues depending on your terminal, because many terminal programs buffer STDIN by default. To test if that is the problem, you can pipe in commands. So, for my toy above,

perl -E'$|=1;print,sleep 1 for 0..9' | perl script.pl
[download]

will slowly print 0 - 9 on the screen, one character a second. For your case, you might want to try pausing and unpausing music once per second.

TLDR: use IO::Handle; and $FIFO->autoflush(1); will set the pipe to hot.

---

#11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.

I added the autoflush ahd its module -- still effect is the same. -- Repetings became necessary up to 7 instead up to 3 w/ the shell version.

I have no ideas what to do except to find the piece of code i have written long time ago for such a task -- that i remembere worked perfect. But do not know where the code is.

Here are the last changes:

use warnings;
use strict;
use utf8::all;
use POSIX qw( mkfifo );

mkfifo( $svitok_truby, 0700 ) || die 'Ошиб&#10
+82;а создания &
+#1090;рубы  '.$svitok_truby.'  : '.$!;
local $SIG{CHLD} = "IGNORE";

# Родитель.
if( $nomer_vosproizvodyshchego_protsessu=fork ){

  use IO::Handle;

  open( $FIFO, '>'.$svitok_truby ) || die 'Не о&#109
+0;крыть труб&#1
+091; '.$svitok_truby.' на запи&#1
+089;ь : '.$!;

  # Same thing? -- I.e. not working?
  $|=1;
  $FIFO->autoflush( 1 );

  use Term::ReadKey;
  ReadMode 'cbreak';

  while( 1 ){

    $knopka=&ReadKey( 0 );

    if( $knopka eq ' ' ){
      print $FIFO 'pause';

    }elsif( $knopka eq '0' ){
      print $FIFO 'quit';
      last;
    }
  }

# Ребёнок.
}else{
  for( $i=0; $i<=$#svitok_na_vosproizvedenie; $i++ ){
    system( '/usr/bin/mplayer -slave -input file='.$svitok_truby.' '.$
+svitok_na_vosproizvedenie_kom[$i] );
  }
}

ReadMode 'normal';
close( FIFO );
unlink $svitok_truby;
[download]

Thanks for your answers.