Question

anyone able to help with perl?

Answer 1

I need to write a program, that is able to print out the last 2 lines of a file from the command line

Answer 2

I did not test the code, it should however in theory work, as there is no reason for it not to. If I might voice my opinions, why would you use Perl to do this it is impractical.

```
#!/usr/bin/perl

use strict;
use warnings;

my $file = 'kmikazuki.txt';
open my $info, $file or die "Could not open $file: $!";

my @lines = <$info>;
print @lines[@lines - 2 .. $#lines];

close $info;
```

Explanation of what I actually did:
I used Perl to read all the lines from the file, in this case kmikazuki.txt into an array, and then used Perl to print the last two lines of that file.

Cons:
Not the most memory efficient method.

Fix:
There is a module for it: File::ReadBackwards, thank God for CPAN.

Answer 3

can you explain to me print @lines[@lines - 2 .. $#lines];

Answer 4

what

print @lines[@lines - 2 .. $#lines];

mean?

Answer 5

like tell me what it means in plain english

Answer 6

Sorry, I was away from my keyboard.

It tells Perl to read the array and print the last two lines of the array. If you do not want to use arrays there is another method you can do, but it is significantly less memory efficient.

Answer 7

print @lines[@lines - 2 .. $#lines];
@lines = array of lines

Answer 8

what does [@lines -2] mean?

Answer 9

like what does " - " mean in perl?

Answer 10

@lines - 2 selects which lines we want to print.

- is an operator, making it print the last two lines rather than first two.
To print the first two use '+'. You can switch operands in Perl safely I think.

Answer 11

why the @line[...] at the begining?

Answer 12

It makes Perl print readable human text rather than something like:
ARRAY(0xead938)

Answer 13

can you explain this code to me?

Answer 14

i need to delete it fast

Answer 15

you saw the link yet?

Answer 16

I don't understand that Perl code, probably because I didn't write it and Perl code is hard for me to understand if someone else wrote it. I am an idiot basically.

It seems that is Perl code doing something with command line arguments. (Hinted by @ARGV.)

That's as much as I can tell.

Answer 17

are you on unix ?

Answer 18

if so, you may use the shell command `tail` for this, perl is not needed

Answer 19

@ganeshie8 is so right.

Answer 20

yeah, but i had to implement the tail command. i finish it already

can you guys explain to me what this means:

push @files, $arg;

Answer 21

@files = ();

push @files, $arg;

Answer 22

does @files = (); => means the file is empty?

Answer 23

@files is an array

$arg is a scalar

Answer 24

yes, its like `declaring` the empty array `@files`

Answer 25

`@` refers to array

`$` refers to scalar

Answer 26

what does push @files, $arg; ?
push the array of empty files onto the scalar argument?

Answer 27

its the other way, visualize below :

`@files` is an empty basket

`$arg` contains the name of file u want to input to ur perl program

`push @files, $arg` pushes the name of file into the basket @files