Loop through file in perl and remove strings with less than 4 characters - perl

Question

I am trying to bring a file loop through it and remove any strings that have less than four characters in it and then print the list. I come from a javascript world and perl is brand new to me.
use strict;
use warnings;
sub lessThan4 {
open( FILE, "<names.txt" );
my #LINES = <FILE>;
close( FILE );
open( FILE, ">names.txt" );
foreach my $LINE ( #LINES ) {
print FILE $LINE unless ( $LINE.length() < 4 );
}
close( FILE );
}

Answer 1

use strict;
use warnings;
# automatically throw exception if open() fails
use autodie;
sub lessThan4 {
my #LINES = do {
# modern perl uses lexical, and three arg open
open(my $FILE, "<", "names.txt");
<$FILE>;
};
# remove newlines
chomp(#LINES);
open(my $FILE, ">", "names.txt");
foreach my $LINE ( #LINES ) {
print $FILE "$LINE\n" unless length($LINE) < 4;
# possible alternative to 'unless'
# print $FILE "$LINE\n" if length($LINE) >= 4;
}
close($FILE);
}

Answer 2

You're basically there. I hope you'll find some comments on your code useful.
# Well done for including these. So many new Perl users don't
use strict;
use warnings;
# Perl programs traditionally use all lower-case subroutine names
sub lessThan4 {
# 1/ You should use lexical variables for filehandles
# 2/ You should use the three-argument version of open()
# 3/ You should always check the return value from open()
open( FILE, "<names.txt" );
# Upper-case variable names in Perl are assumed to be global variables.
# This is a lexical variable, so name it using lower case.
my #LINES = <FILE>;
close( FILE );
# Same problems with open() here.
open( FILE, ">names.txt" );
foreach my $LINE ( #LINES ) {
# This is your biggest problem. Perl doesn't yet embrace the idea of
# calling methods to get properties of a variable. You need to call
# length() as a function.
print FILE $LINE unless ( $LINE.length() < 4 );
}
close( FILE );
}
Rewriting to take all that into account, we get the following:
use strict;
use warnings;
sub less_than_4 {
open( my $in_file_h, '<', 'names.txt' ) or die "Can't open file: $!";
my #lines = <$in_file_h>;
close( $in_file_h );
open( my $out_file_h, '>', 'names.txt' ) or die "Can't open file: $!";
foreach my $line ( #lines ) {
# Note: $line will include the newline character, so you might need
# to increase 4 to 5 here
print $out_file_h $line unless length $line < 4;
}
close( $out_file_h );
}

Answer 3

I am trying to bring a file loop through it and remove any strings that have less than four characters in it and then print the list.
I suppose you need to remove strings from the file which are less than 4 chars in length.
#!/usr/bin/perl
use strict;
use warnings;
open ($FH, "<", "names.txt");
my #final_list;
while (my $line = <$FH>) {
map {
length($_) > 4 and push (#final_list, $_) ;
} split (/\s/, $line);
}
print "\nWords with more than 4 chars: #final_list\n";

Answer 4

#Please try this one:
use strict;
use warnings;
my #new;
while(<DATA>)
{
#Push all the values less than 4 characters
push(#new, $_) unless(length($_) > '4');
}
print #new;
__DATA__
Williams
John
Joe
Lee
Albert
Francis
Sun