Split on . (dot)

fo0 has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Array empty by barrd (Canon) on Oct 05, 2003 at 13:04 UTC
Hi foO, If I understand you correctly you guessed right why `@t` is empty because you needed to escape the fullstop (dot ".") in `split`. Try something like this: `#!/usr/bin/perl -w use strict; my $ip = "192.168.2.34"; my @t = split(/\./, $ip); my $x = @t; print "Number of elements in array: $x\n"; print "Content of array: @t\n";` [download] As a beginner now would be a good time to learn to `use strict` and `warnings` (`-w` flag after shebang). These are handy tools for debugging your future scripts. update: changed text slightly because the node got retitled.	[reply] [d/l] [select]
Re: Array empty by delirium (Chaplain) on Oct 05, 2003 at 14:31 UTC
Two things that help in deducing what's going on with a split function are to tell perl to keep the delimiter matches as elements of the list it returns, and to print out the array line by line rather than with a `print "@t\n";` This is how I would attack the problem: `#!/usr/bin/perl print "Entrez votre ip :"; $ip=<STDIN>; @t=split(/(.)/,$ip); # Surround the delimiter in (), then the # regexp matches become array elements print scalar @t,"\n"; # Don't waste a variable print "[$_]\n" for @t; # Surround each match by brackets, # print each match on its own line.` [download] Then your output becomes: `Entrez votre ip :21.23 11 [] [2] [] [1] [] [.] [] [2] [] [3] [ ]` [download] "Oh, each byte was a match," says I. Changing `@t=split(/(.)/,$ip);` to `@t=split(/(\.)/,$ip);` gives: `Entrez votre ip :21.23 3 [21] [.] [23 ]` [download] OK, good. Now we need to get rid of that line feed, and take the delimiter out of the array. Final code: `#!/usr/bin/perl print "Entrez votre ip :"; $ip=<STDIN>; @t=split(/[.\n]/,$ip); # Don't need \. for period in [ ] print scalar @t,"\n"; print "[$_]\n" for @t;` [download] Which outputs: `Entrez votre ip :21.23 2 [21] [23]` [download] Was that what you were looking for?	[reply] [d/l] [select]
Re^2: Array empty by Aristotle (Chancellor) on Oct 05, 2003 at 18:39 UTC
To get rid of the newline you probably should use chomp instead of putting it in the list of delimiters. Makeshifts last the longest.	[reply]
Re: Array empty by arno (Scribe) on Oct 05, 2003 at 13:09 UTC
hi, In you code, split returns all fields found in $ip using '.' metacharacter as a delimiter. '.' metacharacter matches almost any character but newline. As a consequence,@t will contain invisible characters as NUL character and \n. When you do : `map { print ord $_,"\n" } split(/./, $ip);` [download] You 'll print the ascii code of each element in the returned list by split function. Here's the output i get : 0 0 0 0 0 10 0 is the ascii NUL and 10 is the newline character. I hope you understand these explanations, Arnaud	[reply] [d/l]
Re: Re: Array empty by bart (Canon) on Oct 05, 2003 at 14:11 UTC
Close. But ord($_) returns 0 not because it contains a null byte, but because it is an empty string. `print ord("");` [download] prints: `0` (Where on earth would he be getting null bytes from?) Indeed, the resulting array he's getting after doing `$ip = "21.23\n"; @t = split /./, $ip;` [download] is ("", "", "", "", "", "\n") The explanation: every character in the input string, except the newline, is used as a split delimiter. Thus you get, as a result, the stuff between those characters, which is nothing every time, except at the last character.	[reply] [d/l] [select]


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