Filehandles - opening/closing a filehandle

yabba has asked for the wisdom of the Perl Monks concerning the following question:

I just wanted to say that I'm a new PERL programmer and I have lots of things to learn. I've been working on this program for some time. I'm having trouble with opening and closing and writing to my file. Here's what I got so far:

use strict;
my @data;
my $avg;
my $dev;
my $std;
my $tmp;
my $grade;
my $line;

open(IN, "pa5c.dat") || die ("Can't open file $!\n");
while($line = <IN>){
          chomp ($line);
         my $tmp = [split /:/];
          $avg += $tmp->[1];
          push @data, $tmp;

}
$avg = scalar(@data) ? $avg /= @data : 0;


my $std = 0;
for (@data) { $std += abs($_->[1] - $avg) }
        $std = scalar(@data) ? $std /= @data : 0;

open(OUT, ">pa5c.dat") || die ("Can't open file $!\n");
        for (@data) {
          my $grade;
          my $dev = ($_->[1] - $avg) / $std;
          if ($dev >= 1) { $grade = 'A' }
          elsif ($dev >= (1/3)) { $grade = 'B' }
         elsif ($dev >= (-1/3)) { $grade = 'C' }
         elsif ($dev > -1) { $grade = 'D' }
         else { $grade = 'E' }
         print OUT join (':', $_->[0], $_->[1], $grade) . "\n";
}

close OUT;


__END__#pa52.pl
[download]

The pa5c.dat file contains:

Smith:70
Jones:74
Rider:80
High:82
Billie:68
Smithsonville:76
[download]

Now if my program runs correctly, my program should assign letter grades to the students.

Comment on Filehandles - opening/closing a filehandle Select or Download Code

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(jptxs) Re: Filehandles - opening/closing a filehandle by jptxs (Curate) on Apr 08, 2001 at 20:02 UTC
could not in good conscience answer this in full for I once was a teacher, too. so let me do two things to point you in the right way. you're on the right track. refine what you have and it will work. break everything down to distinct actions. literally, speak your program out as a paragraph, then break the code up to match the sentances. test each piece on it's own and as they work put them together. look up Elements of Programming with Perl at your local library/bookstore. don't buy it if you don't want, but it has an example almost exactly like this assignment you could model your program from. Hope that helps. `"A man's maturity -- consists in having found again the seriousness one had as a child, at play." --Nietzsche` [download]	[reply] [d/l]
Re: Filehandles - opening/closing a filehandle by rchiav (Deacon) on Apr 08, 2001 at 20:21 UTC
This isn't a response to help you figure out what's going on with your script since I think the previous answers have taken care of that. I just wanted to give you some advice on the questions that you post. It would be to your benifit to try to structure them a little better. For one, you haven't told anyone what happens when you run this. There's actually no question. If you'd provide output, or an error, or what's happening that's unexpected, I think people would be more willing to help. I'd also suggest reading this thread. It has a lot of really good information on how to post good questions. I think you'll find that the people here are some of the most helpful you'll find anywhere, but only if you post appropriately. A little more thought to your questions will go a long way. Good luck with the program... Rich `bash: undo: command not found`	[reply] [d/l]
Re: Filehandles - opening/closing a filehandle by wardk (Deacon) on Apr 08, 2001 at 20:02 UTC
wrt files, you don't appear to be closing your file before opening it again for write.	[reply]