I have posted this here because I had in the past implemented<>this using different approaches and none where to my satisfaction (made by me :-), I know this is a rather old post, yet this problem is rather difficult one otherwise and the code is almost self explanatory. It is based on sysread almost word for word from the perl cookbook or programming perl, the blocking factor is set to 2 bytes, in the event I want port this to win 32 'CRLF'.

sub getcmd {
my $cin='';
my $buf='';
my $len=0;
my @cin=();
local $/=undef;

   while  ($RUN) {
      print(STDERR ' ');
      $buf='';
      $len=0;
      while ($len=sysread(STDIN,$buf,2)) {
         if (! defined($len)) {
            next if ($! =~ /^Interrupted/);
            fatal(0xff,"system read fault",$!);
         }
         $cin.=$buf;
         last if (rindex($buf,"\n",0) > -1);
      }
      chomp($cin);
      if ($cin) {
         @cin=split(/\s+/,$cin);
         print(STDERR "CIN: $cin\n") if $VRB;
         last;
      } else {
         $RUN--;
         unless ($RUN) {
            print(STDERR "EXIT: timeout no activity\n") if $VRB;
            print(0x11);
         }
         sleep 1
      }
   }

   return(@cin);
}
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