perl split delimiter from file line by line - arrays

Question

I have a text file named 'dataexample' with multiple line like this:
a|30|40
b|50|70
then I split the delimiter with this code:
open(FILE, 'dataexample') or die "File not exist";
while(<FILE>){
my #record = split(/\|/, $_);
print "$record[0]";
}
close FILE;
when I print "$record[0]" , this is what I got:
ab
what I expect :
a 30 40
so when I do print "$record[0][0]" I expect the output to be: a
Where I got it wrong?

Answer 1

Your loop while ( <FILE> ) { ... } reads a single line at a time from the file handle and puts it into $_
my #record = split(/\|/, $_) splits that line on pipe characters |, so since the first line is "a|30|40\n", #record will now be 'a', '30', "40\n". The newline read from the file remains, and you should use chomp to remove it if you don't want it there
So now $record[0] is a, which you print, and then go on to read the next line in the file, setting #record to 'b', '50', "70\n" this time. Now $record[0] is b, which you also print, showing ab on the console
You've now reached the end of the file, so the while loop terminates
It sounds like you're expecting a two-dimensional array. You can do that by pushing each array onto a main array each time you read a record, like this
use strict;
use warnings 'all';
open my $fh, '<', 'dataexample' or die qq{Unable to open "dataexample" for input: $!};
my #data;
while ( <$fh> ) {
chomp;
my #record = split /\|/;
push #data, \#record;
}
print "#{$data[0]}\n";
print "$data[0][0]\n";
output
a 30 40
a
Or, more concisely, like this, which produces exactly the same result but may be a little advanced for you
use strict;
use warnings 'all';
open my $fh, '<', 'dataexample' or die qq{Unable to open "dataexample" for input: $!};
my #data = map { chomp; [ split /\|/ ] } <$fh>;
print "#{$data[0]}\n";
print "$data[0][0]\n";
Some points to know about your own code
You must always use strict and use warnings 'all' at the top of every Perl program you write. It's a measure that will uncover many simple mistakes that you may not otherwise notice
You should use lexical filehandles together with the three-parameter form or open. And an open may fail for many other reasons that the file not existing, so you should include the built-in $! variable in your die string to say why it failed
Don't forget to chomp each record read from a file unless you want to keep then trailing newline or it doesn't matter to you
You will be able to write more concise code if you get used to using the default variable $_. For instance, the second parameter to split is $_ by default, so split(/\|/, $_) may be written as just split /\|/
You can use Data::Dumper to display the contents of your variables, which will help you to debug your code. Data::Dump is superior, but it isn't a core module so you will probably have to install it before you can use it in your code

Answer 2

You have to use
print "$record[1]";
print "$record[2]";
As they are stored in consecutive index values.
or
If you want to print the entire thing you can just do
print "#record\n";

Answer 3

You are printing the value at the first index in the array each time through the loop, and without the new line. So you get the first value from each line, right next to each other on the same line, thus ab.
Print the whole array, under quotes, with the new line. with your program changed a bit
use strict;
use warnings;
my $file = 'dataexample';
open my $fh, '<', $file or die "Error opening $file: $!";
while (<$fh>) {
chomp;
my #record = split(/\|/, $_);
print "#record\n";
}
close $fh;
With the quotes the elements are printed with spaces added between them so you get
a 30 40
b 50 70
If you print without quotes the elements get printed without extra spaces, so
this
print #record, "\n";
over the whole loop prints
a3040
b5070
If you don't have the new line "\n" either, it is all printed on one line so this
print #record;
altogether prints
a3040b5070
As for $record[0][0], this is not valid for the array you have. This would print from a two-dimensional array. Take, for example
my #data = ( [1.1, 2.2], [10, 20] );
This array #data has at its first index a reference to an array -- more precisely, an anonymous array [1.1, 2.2]. Its second element is an anonymous array [10, 20]. So $data[0][0] is: the first element of #data (so the first of the two anonymous arrays inside), and then the first element of that array, thus 1.1. Likewise $data[1][1] is 20.
Thanks to Sobrique for the comment.
But you don't have this in your program. When you split data into an array
while(<FILE>){
my #record = split(/\|/, $_);
# ...
}
it creates a new array named #record every time through the loop. So #record is a normal array, not two-dimensional. For that the syntax $record[0][0] doesn't mean much.

Answer 4

I think you're trying to create a 2d array, whereby each element contains all the pipe delimited items from each line of your input:
my #record;
while(<DATA>){
chomp;
my #split = split(/\|/);
push #record, [#split];
}
print "#{$record[0]}\n";
a 30 40

Answer 5

record[0] has the contents of column 1 - 'a' on the first iteration of the loop, 'b' on the second. record[1] has column 2 and so on. You put the print statement, print "record[0]" in the loop so you get 'a' printed in the first iteration and 'b' in the second.
To get what you wanted you need to replace you print statement with;
print join " ", #record, "\n";