numbering lines problem

WisDomSeeKer34 has asked for the wisdom of the Perl Monks concerning the following question:

I was advised to come here: http://www.linuxquestions.org/questions/showthread.php?p=5271797#post5271797
This is the code:


#!/usr/bin/perl

use warnings;

for ($x = 1; $x < 10; $x++) {

if ($_ =~ /^\d/) {$y = $y + 1;}    # if the line does start with a num
+ber, ignore it. 
if ($_ != /^\d/) {print $y.$x;}    # if the line doesn't start with nu
+mber then print numbers.
}
[download]

After running it: perl counting.pl python.txt I get the following error:
Use of uninitialized value $_ in pattern match (m//) at counting.pl line 7.
Use of uninitialized value $_ in pattern match (m//) at counting.pl line 8.
Use of uninitialized value $_ in numeric ne (!=) at counting.pl line 8.
etc.

Purpose of the program is to line numbers according to chapter:
1.
1.1
1.2
2.
2.1
2.2

Comment on numbering lines problem Select or Download Code

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Re: numbering lines problem by toolic (Bishop) on Nov 19, 2014 at 13:53 UTC
http://www.linuxquestions.org/questions/showthread.php?p=5271797#post5271797 Here is a self-contained version. As pan64 noted, you need to get your lines of input from somewhere (this is why $_ is uninitialized). You should just be able to use `while (<>) {` to read in from your python.txt file. `use warnings; use strict; my $chap; my $sect; while (<DATA>) { if (/^(\d+)/) { $chap = $1; $sect = 0; } else { $sect++; s/^/$chap.$sect /; } print; } __DATA__ 1. Operators Performing simple arithmetic Operating on bitwise values Comparing values Operating on Boolean values Operating on parts of a container with the slice operator Understanding operator precedence 2. Regular Expressions Using the re module Searching with regular expressions` [download] See also: perlintro	[reply] [d/l] [select]
Re^2: numbering lines problem by WisDomSeeKer34 (Sexton) on Nov 19, 2014 at 14:30 UTC
Reading your code, it seems so obvious. Thank you.	[reply]
Re: numbering lines problem by AnomalousMonk (Archbishop) on Nov 19, 2014 at 14:25 UTC
`if ($_ != /^\d/) {print $y.$x;} # if the line doesn't start with number then print numbers.` For future reference, also note that `!~` is "negated match", whereas `!=` is numeric not-equal, hence the warning. See perlop.	[reply] [d/l] [select]