The split and join Functions
Regular expressions can be used to break a string into fields. The
split
function does this and the
join
function glues the pieces back together.
The split Function
The
split
function takes a regular expression and a string and looks
for all occurrences of the regular expression within that string. The
parts of the string that don’t match the regular expression are
returned in sequence as a list of values. For example, here’s
something to parse semicolon-separated fields, such as the
PATH
environment variable:
$line = "c:\\;;c:\\windows\\;c:\\windows\\system;"; @fields = split(/;/,$line); # split $line, using ; as delimiter # now @fields is ("c:\", "", "c:\windows","c:\windows\system")
Note how the empty second field became an empty string. If you don’t want this to happen, match all of the semicolons in one fell swoop:
@fields = split(/;+/, $line);
This matches one or more adjacent semicolons together, so that there is no empty second field.
One common string to split is the
$_
variable, and
that turns out to be the default:
$_ = "some string"; @words = split(/ /); # same as @words = split(/ /, $_);
For this split, consecutive spaces in the string to be split will
cause null fields (empty strings) in the result. A better pattern
would be / +/
, or ideally
/\s+/
, which matches one or more whitespace
characters together. In fact, this pattern is the default
pattern,[55] so if you’re splitting the
$_
variable on whitespace, you can use all the defaults and merely ...
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