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8.9. Processing Variable-Length Text Fields
8.9.1. Problem
You
want to extract variable-length fields from your input.
8.9.2. Solution
Use split with a pattern matching the field
separators.# given $RECORD with field separated by a pattern,
# extract a list of fields
@FIELDS = split(/PATTERN/, $RECORD);
8.9.3. Discussion
The split function takes up to three arguments:
PATTERN, EXPRESSION, and
LIMIT. The LIMIT parameter is
the maximum number of fields to split into. (If the input contains
more fields, they are returned unsplit in the final list element.) If
LIMIT is omitted, all fields (except any final
empty ones) are returned. EXPRESSION gives the
string value to split. If EXPRESSION is omitted,
$_ is split. PATTERN is a
pattern matching the field separator. If PATTERN
is omitted, contiguous stretches of whitespace are used as the field
separator and leading empty fields are silently
discarded. If your input field separator isn't a fixed string, you might want
split to return the field separators as well as
the data by using parentheses in PATTERN to save
the field separators. For instance:split(/([+-])/, "3+5-2");
returns the values:(3, "+", 5, "-", 2)
To split colon-separated records in the style of the
/etc/passwd file, use:@fields = split(/:/, $RECORD);
The classic application of split is
whitespace-separated records:@fields = split(/\s+/, $RECORD);
If $RECORD started with whitespace, this last use
of split would have put an empty string into the
first element of @fields because
split would consider the record to have an initial
empty field. If you didn't want this, you could use this special form
of split:@fields = split(" ", $RECORD);
This behaves like split with a pattern of
/\s+/, but ignores leading whitespace.When the record separator can appear in the record, you have a
problem. The usual solution is to escape occurrences of the record
separator in records by prefixing them with a backslash. See Recipe 1.18.
8.9.4. See Also
The split function in
perlfunc(1) and in Chapter 29 of
Programming Perl; Recipe 1.18
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| 8.8. Reading a Particular Line in a File |  | 8.10. Removing the Last Line of a File |
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