I need to read data from a file into a perl hash (associative array)
table.  The data in the file consists of just a list of names (first
and last names of each person on the same line, and each person on a
different line.)  I need the names to all = 0, too.  So, for example,
once the file is read into the hash table, I should be able to
reference it's value with:

print $hash_table{"name_first name_last"};

And, this should print out 0 (and every record should be 0), because
that's what it was assigned to when the hash was created.  The name
file looks like this:

first_name1 last_name1
first_name2 last_name2
first_name3 last_name3

etc.

Please help!

Hi carl655321

The following little snippet of code should do exactly what you want:

open(IN, "<name_file")
  or die "Couldn't open file for processing: $!";
while (<IN>) {
  chomp;
  $hash_table{$_} = 0;
}
close IN;

Once you've read in your values, the following single line of code
will print them all out for you:

print "$_ = $hash_table{$_}\n" foreach keys %hash_table;


I hope that the above meets your needs. If I've misunderstood your
question, or if you'd like some explanation of how the program works,
please feel free to request a clarification and I'll do my best to get
what you require.


Regards
iaint-ga

---

Request for Answer Clarification by carl655321-ga on 21 Aug 2002 10:32 PDT

iaint,

Thanks for helping with this problem.  The first part of your code
works fine (I guess).  I'm having problems printing it out, though.

I tried your loop, print "$_ = $hash_table{$_}\n" foreach keys
%hash_table;, and I receive this error "Missing $ on loop variable at
asg6.perl line 11.".  I tried to print out just one of records with
this: print table${"record name"};  but I don't get any output.  I was
expecting a 0 since that was what we assigned everything to.

I've double checked the input file, and it's fine.  I also tried
cutting and pasting your code snippet, so I didn't make a typo.  Could
you please double check it, and let me know how to proceed.  Thanks
for your help.

---

Clarification of Answer by iaint-ga on 21 Aug 2002 11:49 PDT

Hi carl655321

Firstly, I'd advise doing what pne-ga suggests in the first comment
below; the solutions he has given should solve the problems you are
having.

If these don't do what you want, leave another clarification and I'll
take a look again.

Regards
iaint-ga

I am very satisfied with this answer; it was _very_ quick, and accurate.  Thank you!

What version of perl are you using? (Running "perl -v" will tell you.)

The "missing $ on loop variable" sounds as if you have an older
version that doesn't like "STATEMENT foreach EXPR".

Try rewriting the code

  print "$_ = $hash_table{$_}\n" foreach keys %hash_table;

as

  foreach (keys %hash_table) {
    print "$_ = $hash_table{$_}\n";
  }

and see whether that makes a difference. If that solves your problem,
then your perl is probably too old. Perhaps you can upgrade? I'd
recommend version 5.6.1, though you can also try 5.8.0 if you don't
mind using a .0 version.

Also, the code

  print table${"record name"};

is incorrect; you probably mean

  print $hash_table{"record name"};

instead (dollar sign before the variable, not after it -- this is Perl
not Visual Basic :)