John W. Krahn wrote:
Mark Day wrote:
Hoping someone can offer some advice on this.
I had an idea to write a script that could open a file
of names, first and last, that would search for the most frequently occurring last names and write out the first and last names of all those that match to a new file. I am a beginner, and of course I have quickly
run up against the limit of my knowledge.
Here's what I've got, (not much), hope it makes some sort of sense
names.txt format: -------------- John Smith Sue Jones Dave Smith Jim Beam Frank Sinatra -------------
#!/usr/bin/perl
use warnings; use strict;
$infile = "names.txt"; $result_file = "most_common.txt";
open (FILE, "$infile") or die, "can't open $infile: $!\n"; open (OUT, ">$result_file") or die, "can't open $result_file: $!\n";
while (<FILE>) {
#this is wrong, i know how do i split the first and last names apart?
my $first_names = $_ split /W*/;
split() returns a list in list context so you need list context on the *left* side of the equals sign. If you don't provide list context then split() will store its results in the @_ array.
Unlike in normal regular expressions * is *not* greedy in split()'s regular expression.
$ perl -le'$_ = q/ one two /; split /W*/; print ">$_<" for @_' > < >o< >n< >e< > < > < > < >t< >w< >o< > <
# how do i get the remainder from the above split into the last names # array bellow
my @last_names =
# Here I'm lost
# My guess is that I need to split first and last apart,
# into a first separate first and last arrays
# then creat a hash table of first and last names, and compare the last # names array to the hash table
# then somehow match the last names that match and print them out
# I don't know how to sort the contents of infile into a hash or compare # them to the contents of a last names array, or even how to split
# first and last into arrays, beyond a vague idea of splitting them on
# white space, with the split function and a regular expression
# That's as far as I've got, any suggestions, tips, etc much appreciated
my %first_last ( 'first' => 'last');
foreach (@last_names =~ %first_last) {
# i know the above is wrong but don't know # how to sort through the hash for matches # or even how to populate the hash
print OUT;
} }
From your description this should do what you want:
#!/usr/bin/perl use warnings; use strict;
my $infile = 'names.txt'; my $result_file = 'most_common.txt';
open FILE, '<', $infile or die "can't open $infile: $!\n"; open OUT, '>', $result_file or die "can't open $result_file: $!\n";
my %first_last; while ( <FILE> ) {
# store the full name in a HoA (see perldsc) # using the last name as the key.
push @{ $first_last{ (split)[ -1 ] } }, $_; }
# this will print out the full names sorted by the number of # entries in the array with the most frequent last names first.
for my $key ( sort { @{ $first_last{ $b } } <=> @{ $first_last{ $a } } } keys %first_last ) {
print OUT for @{ $first_last{ $key } };
}
__END__
Thanks John, I'm going to have a close look at what you've done here,
and will be back to ask some silly questions when I have tried to fully comprehend your code. It'll take me a little while to digest.
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