#! /usr/local/bin/perl
pipe(read_1,write_1);  # open pipe 1
pipe(read_2,write_2);  # open pipe 2

# unbuffer all i/o on the pipes
$old_h=select(read_1);
$|=1;
select(read_2);
$|=1;
select(write_1);
$|=1;
select(write_2);
$|=1;
select($old_h);
$|=1;

if ($pid=fork) {
    # the parent do not do anything here} 
    # so close off the read_1 and write_2
    # hence wirte to write_1 and get results off read_2
    $old_h=select(read_2);
    $|=1;
    select(write_1);
    $|=1;
    select($old_h);
    close(read_1);
    close(write_2);
} elsif (defined $pid) {
    # this is the child so...
    # close off read_2 and write_1
    # redirect stdin to read_1 and stdout to write_2
    # then start up the work code
    $old_h=select(read_1);
    $|=1;
    select(write_2);
    $|=1;
    select($old_h);
    close(read_2);
    close(write_1);

    close(STDOUT);
    open(STDOUT,">& write_2");
    select(STDOUT);
    
    close(STDIN);
    open(STDIN,"<& read_1");
    close(read_1);
 
    sleep(1); 

    system("/data/02/steve/mag_stuff/calc_mag") || print ("Is this working?\n");
    die "ending child\n";
}


# 1. need lat lon depth of the event
# 2. the file to read and calc the magnitudes

if ($#ARGV<3) {
    print stderr "Need 4 input arguements ...\n";
    print stderr "latitude longitude depth amplitude_file\n";
}

$lat=$ARGV[0];
$lon=$ARGV[1];
$depth=$ARGV[2];
$file=$ARGV[3];

open (in_file,"$file");

while (<in_file>) {

    if (!/^\#/ && length($_)>1) {
	($station,$type,$amplitude,$period,$index)=split;
	$station=substr($station,0,length($station)-3);
	$type=substr($type,0,2);
	$frequency=sprintf "%7.4lf",1/$period if ($period !=0);
	print "$station $type $amplitude $frequency $lat $lon $depth\n";
	print write_1 "$station $type $amplitude $frequency $lat $lon $depth\n";
	$new_line=<read_2>;
	print $new_line;
	@n=split(/\s+/,$new_line);
	$s_mag=$n[$#n];
	$st_mag{$n[1]}+=$s_mag;
	$sm_count{$n[1]}+=1;
    }
}

foreach $f (keys(%sm_count)) {
    $n_mag=$st_mag{$f}/$sm_count{$f} if ($sm_count{$f}!=0);
    printf "$f %4.2f for $sm_count{$f} readings\n",$n_mag;
}