NAME
Parse::CSV - Highly flexible CSV parser for large files
SYNOPSIS
# Simple headerless comma-seperated column parser
my $simple = Parse::CSV->new(
file => 'file.csv',
);
while ( my $array_ref = $simple->fetch ) {
# Do something...
}
... or a more complex example...
# Parse a colon-seperated variables file from a handle as a hash
# based on headers from the first line.
# Then filter, so we emit objects rather than the plain hash.
my $objects = Parse::CSV->new(
handle => $io_handle,
sep_char => ';',
names => 1,
filter => sub { My::Object->new( $_ ) },
);
while ( my $object = $objects->fetch ) {
$object->do_something;
}
DESCRIPTION
Surely the CPAN doesn't need yet another CSV parsing module.
Text::CSV_XS is the standard parser for CSV files. It is fast as hell,
but unfortunately it can be a bit verbose to use.
A number of other modules have attempted to put usability wrappers
around this venerable module, but they have all focused on parsing the
entire file into memory at once.
This method is fine unless your CSV files start to get large. Once that
happens, the only existing option is to fall back on the relatively slow
and heavyweight XML::SAXDriver::CSV module.
Parse::CSV fills this functionality gap. It provides a flexible and
light-weight streaming parser for large, extremely large, or arbitrarily
large CSV files.
Main Features
Stream-Based Parser - All parsing a line at a time.
Array Mode - Parsing can be done in simple array mode, returning a
reference to an array if the columns are not named.
Hash Mode - Parsing can be done in hash mode, putting the data into a
hash and return a reference to it.
Filter Capability - All items returned can be passed through a custom
filter. This filter can either modify the data on the fly, or drop
records you don't need.
Writing Filters
A Parse::CSV filter is a subroutine reference that is passed the raw
record as $_, and should "return" the alternative or modified record to
return to the user.
The null filter (does not modify or drop any records) looks like the
following.
sub { $_ };
A filter which reversed the order of the columns (assuming they are
passed as an array) might look like the following.
sub { return [ reverse @$_ ] };
To drop the record, you should return "undef" from the filter. The
parser will then keep pulling and parsing new records until one passes
the filter.
# Only keep records where foo is true
sub { $_->{foo} ? $_ : undef }
To signal an error, throw an exception
sub {
$_->{foo} =~ /bar/ or die "Assumption failed";
return $_;
}
METHODS
new
The "new" constructor creates and initialise a new CSV parser.
It takes a number of params.
To specify the CSV data source, you should provide either the "file"
param, which should be the name of the file to read, or the "handle"
param, which should be a file handle to read instead.
The actual parsing is done using Text::CSV_XS. Any of its
constructor/parsing params can also be provided to this "new" method,
and they will be passed on.
Alternatively, they can be passed as a single "HASH" reference as the
"csv_attr" param. For example:
$parser = Parse::CSV->new(
file => 'file.csv',
csv_attr => {
sep_char => ';',
quote_char => "'",
},
);
An optional "names" param can be provided, which should be an array
reference containing the names of the columns in the CSV file.
$parser = Parse::CSV->new(
file => 'file.csv',
names => [ 'col1', 'col2', 'col3' ],
);
If the "names" param is provided, the parser will map the columns to a
hash where the keys are the field names provided, and the values are the
values found in the CSV file.
If the "names" param is not provided, the parser will return simple
array references of the columns.
If the "names" param is true and not a reference, the names will be
automatically determined by reading the first line of the CSV file and
using those values as the field names.
The optional "filter" param will be used to filter the records if
provided. It should be a "CODE" reference or any otherwise callable
scalar, and each value parsed (either array reference or hash reference)
will be passed to the filter to be changed or converted into an object,
or whatever you wish.
Returns a new Parse::CSV object, or throws an exception (dies) on error.
fetch
Once a Parse::CSV object has been created, the "fetch" method is used to
parse and return the next value from the CSV file.
Returns an "ARRAY", "HASH" or the output of the filter, based on the
configuration of the object, or "undef" in a variety of situations.
Returning "undef" means either some part of the parsing and filtering
process has resulted in an error, or that the end of file has been
reached.
On receiving "undef", you should the "errstr" method. If it is a null
string you have reached the end of file. Otherwise the error message
will be returned. Thus, the basic usage of Parse::CSV will look like the
following.
my $parser = Parse::CSV->new(
file => 'file.csv',
);
while ( my $value = $parser->fetch ) {
# Do something...
}
if ( $parser->errstr ) {
# Handle errors...
}
row
The "row" method returns the current row of the CSV file.
This is a one-based count, so when you first create the parser, the
value of "row" will be zero (unless you are using "names" on automatic
in which case it will be 1).
combine
$status = $csv->combine(@columns);
The "combine" method is provided as a convenience, and is passed through
to the underlying Text::CSV_XS object.
string
$line = $csv->string;
The "string" method is provided as a convenience, and is passed through
to the underlying Text::CSV_XS object.
print
$status = $csv->print($io, $columns);
The "print" method is provided as a convenience, and is passed through
to the underlying Text::CSV_XS object.
fields
@fields = $csv->fields;
The "fields" method is provided as a convenience, and is passed through
to the underlying Text::CSV_XS object. It shows the actual row as an
array.
names
# Get the current column names in use
my @names = $csv->names;
# Change the column names on the fly mid stream
$csv->names( 'fn1', 'fn2' );
The "names" method gets or sets the column name mapping for the parser.
errstr
On error, the "errstr" method returns the error that occured.
If the last action was NOT an error, returns the null string ''.
SUPPORT
Bugs should always be reported via the CPAN bug tracker at
<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Parse-CSV>
For other issues, or commercial enhancement or support, contact the
author.
AUTHORS
Adam Kennedy <adamk@cpan.org>
CONTRIBUTORS
Uwe Sarnowski <uwes@cpan.org>
SEE ALSO
Text::CSV_XS, <http://ali.as/>
COPYRIGHT
Copyright 2006 - 2012 Adam Kennedy.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
The full text of the license can be found in the LICENSE file included
with this module.