Read specific column in perl - perl

Question

I'm new in perl. I have below text file and from there I want only one Time column and next columns are values. How can I create a text file with my desire output in perl.
Time Value Time Value Time Value
1 0.353366497 1 0.822193251 1 0.780866396
2 0.168834182 2 0.865650713 2 0.42429447
3 0.323540698 3 0.865984245 3 0.856875894
4 0.721728497 4 0.634773162 4 0.563059042
5 0.545131335 5 0.029808531 5 0.645993399
6 0.143720835 6 0.949973296 6 0.14425803
7 0.414601876 7 0.53421424 7 0.826148814
8 0.194818367 8 0.942334356 8 0.837107013
9 0.291448263 9 0.242588271 9 0.939609775
10 0.500159997 10 0.428897293 10 0.41946448
I've tried below code:
use strict;
use warnings;
use IO::File;
my $result;
my #files = (q[1.txt],q[2.txt],q[3.txt]);
my #fhs = ();
foreach my $file (#files) {
my $fh = new IO::File $file, O_RDONLY;
push #fhs, $fh if defined $fh;
}
while(1) {
my #lines = map { $_->getline } #fhs;
last if grep { not defined $_ } #lines[0..(#fhs-1)];
my #result=join(qq[\t], map { s/[\r?\n]+/ /g; $_ } #lines ) . qq[\r\n];
open (MYFILE, '>>Result.txt');
print (MYFILE "#result");
close (MYFILE);
}

Answer 1

I'd go with split.
use warnings;
use strict;
open (my $f, '<', 'your-file.dat') or die;
while (my $line = <$f>) {
my #elems = split ' ', $line;
print join "\t", #elems[0,1,3,5];
print "\n";
}

Answer 2

This is a one-liner; no need to write a script:
$ perl -lanE '$,="\t"; say #F[0,1,3,5]' 1.txt 2.txt 3.txt
If you like, you can shorten it to:
$ perl -lanE '$,="\t"; say #F[0,1,3,5]' [123].txt

Answer 3

Right now, you're just concatenating the lines of the files together. If that doesn't give you the output you like, you need to chop some columns out.
Since your output looks like you have tab delimited files as input, I split the lines coming in by tabs. And since you only wanted the second column, I only take the column at the first offset from the split.
my $line_num = 0;
while(1) {
my #lines = map { $_->getline } #fhs;
last if grep { not defined $_ } #lines[0..$#fhs];
$line_num++;
my #rows = map { [ split /\t/ ] } #lines;
my $time_val = $rows[0][0];
die "Time values are not all equal on line #$line_num!"
if grep { $time_val != $_->[0] } #rows
;
my $result = join( q[\t], $time_val, map { $_->[1] } #rows );
open (MYFILE, '>>Result.txt');
print (MYFILE "$result\n");
close (MYFILE);
}
Of course, there is no reason to do custom coding to split delimited columns:
use Text::CSV;
...
my $csv = Text::CSV->new( { sep_char => "\t" } );
while(1) {
my #rows = map { $csv->getline( $_ ) } #fhs;
last if grep { not defined $_ } #rows[0..$#fhs];
my ( $time_val, #time_vals ) = map { $_->[0] } #rows;
my #values = map { $_->[1] } #rows;
die "Time values are not all equal on line #$line_num!"
if grep { $time_val != $_ } #time_vals
;
my $result = join( q[\t], $time_val, #values );
...
}

Answer 4

use strict;
use warnings;
open(FH,"<","a.txt");
print "=========== A File content =========== \n";
my $a = `cat a.txt`;
print "$a\n";
my #temp = <>;
my (#arr, #entries, #final);
foreach ( #temp ) {
#arr = split ( " ", $_ );
push #entries, #arr;
}
close FH;
my #entries1 = #entries;
for(my $i = 7; $i<=$#entries; $i=$i+2) {
push #final, $entries[$i];
}
my $size = scalar #final;
open FH1, ">", "b.txt";
print FH1 "Time \t Value\n";
for(my $i = 0; $i < $size; $i++) {
my $j = $i+1;
print FH1 "$j \t $final[$i]\n";
}
close FH1;
print "============ B file content ===============\n";
my $b = `cat b.txt`;
print "$b";
O/P:
=========== A File content ===========
Time Value Time Value Time Value
1 0.353366497 1 0.822193251 1 0.780866396
2 0.168834182 2 0.865650713 2 0.42429447
3 0.323540698 3 0.865984245 3 0.856875894
4 0.721728497 4 0.634773162 4 0.563059042
5 0.545131335 5 0.029808531 5 0.645993399
6 0.143720835 6 0.949973296 6 0.14425803
7 0.414601876 7 0.53421424 7 0.826148814
8 0.194818367 8 0.942334356 8 0.837107013
9 0.291448263 9 0.242588271 9 0.939609775
10 0.500159997 10 0.428897293 10 0.41946448
============ B file content ===============
Time Value
1 0.353366497
2 0.822193251
3 0.780866396
4 0.168834182
5 0.865650713
6 0.42429447
7 0.323540698
8 0.865984245
9 0.856875894
10 0.721728497
11 0.634773162
12 0.563059042
13 0.545131335
14 0.029808531
15 0.645993399
16 0.143720835
17 0.949973296
18 0.14425803
19 0.414601876
20 0.53421424
21 0.826148814
22 0.194818367
23 0.942334356
24 0.837107013
25 0.291448263
26 0.242588271
27 0.939609775
28 0.500159997
29 0.428897293
30 0.41946448