Push File contents into the array using perl - perl

Question

Suppose this is the file I am reading
hey how are you
I am fine thank you
Here I want to store the contents of file into an array using one while loop so that I can easily use the array later and need not to open close file again.
Code
use warnings;
use strict;
my #point1;
my #point ;
my $log1= "log1.log";
open(IN1, "<$log1" ) or die "Could not open file $log1: $!";
while (my $line = <IN1>) {
#point = split " ",$line;
push(#point1,#point);
push(#point1,"\n");
}
print "$point1[0] 2nd\n";
close IN1;
Output
hey 2nd
I want output like below if I am printing outside while loop.
Output I want:
hey 2nd
I 2nd
What changes should I make here?

Answer 1

You are pushing all the words in the file onto the same list, which will make it difficult to tell them apart.
push(#point1,#point);
This is the same as doing
#point1 = qw(hey how are you I am fine thank you);
I suspect what you want is a two-dimensional array, so that you afterwards can supply line number and word number and print that word, like this:
print $point1[0][0]; # prints "hey"
To do that, you would do this:
push #point1, \#point; # the backslash makes us get the reference to the array
But then you also have to make sure that all the lines do not point to the same array, as they would when you declare my #point outside of the loop.
my #point; # outside the loop
while (my $line = <IN1>) {
#point = split " ",$line;
push(#point1, \#point); # wrong
}
You would have to declare it inside the loop
while (my $line = <IN1>) {
my #point = split " ",$line; # inside the loop
push(#point1, \#point); # correct
}
Because then it will be a new array reference each loop iteration, one for each new line. But you do not need to use a temporary variable, you can just push the values directly
while (my $line = <IN1>) {
push #point1, [ split " ",$line; ];
}
The square brackets creates a reference to an anonymous array, with the values that are inside it. Afterward you can solve your task like this:
for my $aref (#point1) {
print "$aref->[0] 2nd\n";
}
Or
for my $line_no (0 .. $#point1) {
print "$point1[$line_no][0] 2nd\n";
}

Answer 2

use strict;
use warnings;
use feature qw( say );
my $log1 = "log1.log";
open(my $fh, "<", $log1) # Don't use a global. Use 3-arg open.
or die("Can't open file \"$log1\": $!\n"); # No need for the line number.
my #first_words;
while (my $line = <$fh>) {
# chomp($line); # Not needed with C<< split " " >>, so that was ok.
my #words = split " ", $line; # Declare variable to the scope where they are needed.
push #first_words, $words[0]; # You want the first word of each line.
}
for my $first_word (#first_words) { # Need a loop to print stuff repeatedly.
say "$first_word 2nd";
}
or
use strict;
use warnings;
use feature qw( say );
my #first_words;
while (my $line = <>) {
my #words = split " ", $line;
push #first_words, $words[0];
}
for my $first_word (#first_words) {
say "$first_word 2nd";
}
The second is more flexible. Just pass the desired file name as an argument. It can also handle input via STDIN.

Answer 3

It's not really clear what data structure you're looking for. Here are a few possibilities.
You want each line of your file in an element in the array.
my #array = <$fh>;
You want each line of your file in an element in the array, but you also want the input split into individual words (so you end up with an array of arrays).
my #array = map { [ split ] } <$fh>;
You want the first word of each line in an element in the array.
my #array = map { (split)[0] } <$fh>;
I've mentioned before that you should switch to using the three-arg version of open() and lexical filehandles. So, assume that all of my code examples above are prefaced with:
open my $fh, '<', $log1 or die "Cannot open '$log1': $!\n";
Looking back over your last few questions, I can't help thinking that this is an X/Y question. You're asking for our help with tiny problems that make up part of your code, but actually, we could give far better help if we knew more about the bigger picture.