tailgrep-simple.p6

#!/usr/bin/env perl6

sub spinner() {
  <\ - | - / ->[$++ % 6]
}

sub MAIN($expr, $filename) {
  shell "tput 'civis'";
  my $proc = Proc::Async.new:
    <<tail -f $filename>>;
  my $out = $proc.stdout;
  start react {
    whenever $out.lines.grep( / "$expr" / ) {
      .say
    }
    whenever $out.lines {
      print spinner() ~ "\r";
    }
    whenever signal(SIGINT) {
      shell 'tput cnorm';
      exit;
    }
  }
  await $proc.start;
}