[SOLVED] using Perl's range operation to print from one line to the end of file

captainentropy · 08-23-2013, 06:31 PM

If I have this file:

Code:

A
Header
With 
Unnecessary 
Information
5	9	32	9
1	67	57	97
10	32	8	28

and I want this:

Code:

5	9	32	9
1	67	57	97
10	32	8	28

How would I do that with Perl's range operator?

If I use this script

Code:

#!/usr/bin/perl -w

$data = $ARGV[0];

open (IN, "$data") or die "can't open data:$!";
 
@datafile = <IN>; #Read the data file and store it in an array

close IN;

print @datafile[4 .. 6];

I get

Code:

Information
5	9	32	9
1	67	57	97

But if I want to print every row after (and including) line 4 what would the the second variable in the range operator? I know I could just use an absurdly large number that would extend beyond the length of my file:

Code:

print @datafile[4 .. 10000000];

That works. Or this works:

Code:

$num = @datafile;
print @datafile[4 .. $num];

But what would the the easiest, i.e. something to use for X in @datafile[4 .. X]?

druuna · 08-24-2013, 02:16 AM

You can use $#array_name to get the index of the last element in an array.

Also be aware that, when using a range, the counter starts at 0 and not 1.

Have a look at this:

Code:

#!/usr/bin/perl

use strict ;
use warnings ;

my $infile = $ARGV[0] ;
my @datafile ;

open( IN, "$infile" ) or die "Can't open $infile : $!\n" ;
@datafile = <IN> ;
close $infile ;

print @datafile[ 5 .. $#datafile ] ;

exit 0 ;

Output would look like this:

Code:

5   9   32  9
1   67  57  97
10  32  8   28

captainentropy · 08-25-2013, 02:48 PM

Thanks druuna!