O'Reilly logo

Learning Perl, Second Edition by Randal L. Schwartz, Tom Christiansen

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

7.6. 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.

7.6.1. 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 colon-separated fields, such as in UNIX /etc/passwd files:

$line = "merlyn::118:10:Randal:/home/merlyn:/usr/bin/perl";
@fields = split(/:/,$line); # split $line, using : as delimiter
# now @fields is ("merlyn","","118","10","Randal",
#                 "/home/merlyn","/usr/bin/perl")

Note how the empty second field became an empty string. If you don't want this, match all of the colons in one fell swoop:

@fields = split(/:+/, $line);

This matches one or more adjacent colons together, so 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,[8] so if you're splitting the $_ variable on whitespace, you can use all ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required