The scenario: I have a file with ship id numbers. It gets updated
several times a day (by database query) and I want to find all the
"new_ships" that have been added to it.
sub incremental_update {
print "Doing incremental update.\n";
open $FH, '+<', $ships_file or croak "Cannot open $ships_file!\n";
# Get all the ships in it
my @ships = do { local $/; <$FH> };
my %seen = ( );
my @new_ships = ( );
foreach my $item (@ships) { $seen{$item} = 1 }
# Getall the LLY_NUMS from the table
$sql = qq{ SELECT LLY_NUM FROM AMVER_VESS WHERE ONPLOT_FLAG = 'T' };
$sth = $dbh->prepare( $sql );
$sth->execute or die "Can't execute SQL statement: $DBI::errstr\n";
while ( my @row = $sth->fetchrow->array ) {
foreach my $lly_num (@row) {
unless ( $seen{$lly_num} ) {
# it isn't in %seen, so add it to @new_ships
push( @new_ships, $lly_num );
}
}
print $FH "@new_ships\n";
}
close $FH;
}
I just want to make sure my logic is right on this. If $lly_num isn't in
the %seen hash then it gets added to the @new_ships array. Then all the
new ships are written to the file.
A secondary question: When opening the file is +< correct if I want to
write back to it or should I use +>> ?
Robert
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
