Summing up column values based upon ranges in another file

File 1 has ranges 3-9, 2-6 etc
    3 9
    2 6
    12 20
File2 has values: column 1 indicates the range and column 2 has values.
    1 4
    2 4
    3 5
    4 4
    5 4
    6 1
    7 1
    8 1
    9 4
I would like to calculate the sum of values (file2, column2) for ranges in file1). Eg: If range is 3-9, then sum of values will be 5+4+4+1+1+1+4 = 20

Below is the script for doing the same:

use strict;
use warnings;
use feature qw( say );
use List::Util qw( sum );
my $file1 = 'file1.txt';
my $file2 = 'file2.txt';
my @file2;
{   
   open(my $fh, '<', $file2)
      or die "Can't open $file2: $!\n";
   while (<$fh>) {
      my ($k, $v) = split;
      $file2[$k] = $v;
   }
}
{   
   open(my $fh, '<', $file1)
      or die "Can't open $file1: $!\n";
   while (<$fh>) {
      my ($start, $end) = split;
      say sum grep defined, @file2[$start .. $end];
   }
}

Capitalize every first letter of a word and others to lower case

How can you capitalize(Only first character) each word in a line using perl and change remaining to lower case?

let say there is a file:

> cat temp
hI thIs is woRld

How can we make it

Hi This Is World

Its very simple to do it in perl:

perl -pe 's/(\w+)/\u\L$1/g' your_file

If you want to do it inplace just add a -i flag:

perl -pi -e 's/(\w+)/\u\L$1/g' your_file

Print the next power of 2 for a given number

Below is the program that I have written for printing the next power of 2 for a given number.
The code mostly uses  the bitwise operations in c/c++.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <math.h>

int main ()
{
int num;
scanf("%d",&num);
int count=0;
        if(!((num != 1) && (num&(num-1))))
        {
        printf("%d is already a power of two.\n",num);
        printf("%d is next number power of 2.\n",num*2);
        }
        else
        {
        while((num>>=1)&&(++count));
        printf("%0.0f",pow(2.0,count+1));
        }
}

Sorting files based upon the numeric value before the first field separator

Lets say i have a list of files.

for eg:

ABCD5_Avgsdfgsg.txt
ABCD7_ff.txt
CD8_PKG_CV.txt
ABCD1_11.txt
BCD2_fbefjf.txt
D3_C.txt
ABCD4_123.txt
ABCD10_123.txt

I want to sort these files according to the first number before the first underscore.
I tried with sort but with no proper solution then i tried it in perl and this worked.Hopefully the below helps.

ls -1 | perl -F"_" -lane '$F[0]=~s/[a-zA-Z]//g;$X{$F[0]}=$_;END{foreach(sort {$a<=>$b} keys(%X)){print $X{$_}}}'

tested below:

> ls -1
ABCD10_123.txt
ABCD1_11.txt
ABCD4_123.txt
ABCD5_Avgsdfgsg.txt
ABCD7_ff.txt
BCD2_fbefjf.txt
CD8_PKG_CV.txt
D3_C.txt


> ls -1 | perl -F"_" -lane '$F[0]=~s/[a-zA-Z]//g;$X{$F[0]}=$_;END{foreach(sort {$a<=>$b} keys(%X)){print $X{$_}}}'
ABCD1_11.txt
BCD2_fbefjf.txt
D3_C.txt
ABCD4_123.txt
ABCD5_Avgsdfgsg.txt
ABCD7_ff.txt
CD8_PKG_CV.txt
ABCD10_123.txt
>