Question

我想用<常规词语分拨一个插座,但我已经遇到一些问题。我有这样的说明:

$text=" one two three";

Then I try to split it into alphabetic words:

#@words=split(" ", $text);          #1 this works

@words=split("[^a-zA-Z]", $text);   #2 this doesn t work

for $word (@words){
    printf "word: |$word|
";
}

So the commented method(1) works fine. As expected I get printed:

word: |one|
word: |two|
word: |three|

However with the second method(2) I get this:

word: ||
word: |one|
word: |two|
word: |three|

So although logically the second method should be equivalent to the first one, in practice it doesn t behave the same way. Why is that?

Answer 1

This is a special case in Perl s split() function.

As stated in perldoc:

<代码>split(/PATTERN/,utilr, [limit]>

If PATTERN is omitted, [it] splits on whitespace (after skipping any leading whitespace).

Empty leading fields are produced when there are positive-width matches at the beginning of the string; [...]

As a special case, specifying a PATTERN of space ( ) will split on white space just as split with no arguments does. Thus, split( ) can be used to emulate awk s default behavior, whereas split(/ /) will give you as many initial null fields (empty string) as there are leading spaces.

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