Text::RecordParser(3) User Contributed Perl DocumentationText::RecordParser(3)NAMEText::RecordParser - read record-oriented files
SYNOPSIS
use Text::RecordParser;
# use default record (\n) and field (,) separators
my $p = Text::RecordParser->new( $file );
# or be explicit
my $p = Text::RecordParser->new({
filename => $file,
field_separator => "\t",
});
$p->filename('foo.csv');
# Split records on two newlines
$p->record_separator("\n\n");
# Split fields on tabs
$p->field_separator("\t");
# Skip lines beginning with hashes
$p->comment( qr/^#/ );
# Trim whitespace
$p->trim(1);
# Use the fields in the first line as column names
$p->bind_header;
# Get a list of the header fields (in order)
my @columns = $p->field_list;
# Extract a particular field from the next row
my ( $name, $age ) = $p->extract( qw[name age] );
# Return all the fields from the next row
my @fields = $p->fetchrow_array;
# Define a field alias
$p->set_field_alias( name => 'handle' );
# Return all the fields from the next row as a hashref
my $record = $p->fetchrow_hashref;
print $record->{'name'};
# or
print $record->{'handle'};
# Return the record as an object with fields as accessors
my $object = $p->fetchrow_object;
print $object->name; # or $object->handle;
# Get all data as arrayref of arrayrefs
my $data = $p->fetchall_arrayref;
# Get all data as arrayref of hashrefs
my $data = $p->fetchall_arrayref( { Columns => {} } );
# Get all data as hashref of hashrefs
my $data = $p->fetchall_hashref('name');
DESCRIPTION
This module is for reading record-oriented data in a delimited text
file. The most common example have records separated by newlines and
fields separated by commas or tabs, but this module aims to provide a
consistent interface for handling sequential records in a file however
they may be delimited. Typically this data lists the fields in the
first line of the file, in which case you should call "bind_header" to
bind the field name (or not, and it will be called implicitly). If the
first line contains data, you can still bind your own field names via
"bind_fields". Either way, you can then use many methods to get at the
data as arrays or hashes.
METHODS
new
This is the object constructor. It takes a hash (or hashref) of
arguments. Each argument can also be set through the method of the
same name.
· filename
The path to the file being read. If the filename is passed and the
fh is not, then it will open a filehandle on that file and sets
"fh" accordingly.
· comment
A compiled regular expression identifying comment lines that should
be skipped.
· data
The data to read.
· fh
The filehandle of the file to read.
· field_separator | fs
The field separator (default is comma).
· record_separator | rs
The record separator (default is newline).
· field_filter
A callback applied to all the fields as they are read.
· header_filter
A callback applied to the column names.
· trim
Boolean to enable trimming of leading and trailing whitespace from
fields (useful if splitting on whitespace only).
See methods for each argument name for more information.
Alternately, if you supply a single argument to "new", it will be
treated as the "filename" argument.
bind_fields
$p->bind_fields( qw[ name rank serial_number ] );
Takes an array of field names and memorizes the field positions for
later use. If the input file has no header line but you still wish to
retrieve the fields by name (or even if you want to call "bind_header"
and then give your own field names), simply pass in the an array of
field names you wish to use.
Pass in an empty array reference to unset:
$p->bind_field( [] ); # unsets fields
bind_header
$p->bind_header;
my $name = $p->extract('name');
Takes the fields from the next row under the cursor and assigns the
field names to the values. Usually you would call this immediately
after opening the file in order to bind the field names in the first
row.
comment
$p->comment( qr/^#/ ); # Perl-style comments
$p->comment( qr/^--/ ); # SQL-style comments
Takes a regex to apply to a record to see if it looks like a comment to
skip.
data
$p->data( $string );
$p->data( \$string );
$p->data( @lines );
$p->data( [$line1, $line2, $line3] );
$p->data( IO::File->new('<data') );
Allows a scalar, scalar reference, glob, array, or array reference as
the thing to read instead of a file handle.
It's not advised to pass a filehandle to "data" as it will read the
entire contents of the file rather than one line at a time if you set
it via "fh".
extract
my ( $foo, $bar, $baz ) = $p->extract( qw[ foo bar baz ] );
Extracts a list of fields out of the last row read. The field names
must correspond to the field names bound either via "bind_fields" or
"bind_header".
fetchrow_array
my @values = $p->fetchrow_array;
Reads a row from the file and returns an array or array reference of
the fields.
fetchrow_hashref
my $record = $p->fetchrow_hashref;
print "Name = ", $record->{'name'}, "\n";
Reads a line of the file and returns it as a hash reference. The keys
of the hashref are the field names bound via "bind_fields" or
"bind_header". If you do not bind fields prior to calling this method,
the "bind_header" method will be implicitly called for you.
fetchrow_object
while ( my $object = $p->fetchrow_object ) {
my $id = $object->id;
my $name = $object->naem; # <-- this will throw a runtime error
}
This will return the next data record as a Text::RecordParser::Object
object that has read-only accessor methods of the field names and any
aliases. This allows you to enforce field names, further helping
ensure that your code is reading the input file correctly. That is, if
you are using the "fetchrow_hashref" method to read each line, you may
misspell the hash key and introduce a bug in your code. With this
method, Perl will throw an error if you attempt to read a field not
defined in the file's headers. Additionally, any defined field aliases
will be created as additional accessor methods.
fetchall_arrayref
my $records = $p->fetchall_arrayref;
for my $record ( @$records ) {
print "Name = ", $record->[0], "\n";
}
my $records = $p->fetchall_arrayref( { Columns => {} } );
for my $record ( @$records ) {
print "Name = ", $record->{'name'}, "\n";
}
Like DBI's fetchall_arrayref, returns an arrayref of arrayrefs. Also
accepts optional "{ Columns => {} }" argument to return an arrayref of
hashrefs.
fetchall_hashref
my $records = $p->fetchall_hashref('id');
for my $id ( keys %$records ) {
my $record = $records->{ $id };
print "Name = ", $record->{'name'}, "\n";
}
Like DBI's fetchall_hashref, this returns a hash reference of hash
references. The keys of the top-level hashref are the field values of
the field argument you supply. The field name you supply can be a
field created by a "field_compute".
fh
open my $fh, '<', $file or die $!;
$p->fh( $fh );
Gets or sets the filehandle of the file being read.
field_compute
A callback applied to the fields identified by position (or field name
if "bind_fields" or "bind_header" was called).
The callback will be passed two arguments:
1. The current field
2. A reference to all the other fields, either as an array or hash
reference, depending on the method which you called.
If data looks like this:
parent children
Mike Greg,Peter,Bobby
Carol Marcia,Jane,Cindy
You could split the "children" field into an array reference with the
values like so:
$p->field_compute( 'children', sub { [ split /,/, shift() ] } );
The field position or name doesn't actually have to exist, which means
you could create new, computed fields on-the-fly. E.g., if you data
looks like this:
1,3,5
32,4,1
9,5,4
You could write a field_compute like this:
$p->field_compute( 3,
sub {
my ( $cur, $others ) = @_;
my $sum;
$sum += $_ for @$others;
return $sum;
}
);
Field "3" will be created as the sum of the other fields. This allows
you to further write:
my $data = $p->fetchall_arrayref;
for my $rec ( @$data ) {
print "$rec->[0] + $rec->[1] + $rec->[2] = $rec->[3]\n";
}
Prints:
1 + 3 + 5 = 9
32 + 4 + 1 = 37
9 + 5 + 4 = 18
field_filter
$p->field_filter( sub { $_ = shift; uc(lc($_)) } );
A callback which is applied to each field. The callback will be passed
the current value of the field. Whatever is passed back will become
the new value of the field. The above example capitalizes field
values. To unset the filter, pass in the empty string.
field_list
$p->bind_fields( qw[ foo bar baz ] );
my @fields = $p->field_list;
print join ', ', @fields; # prints "foo, bar, baz"
Returns the fields bound via "bind_fields" (or "bind_header").
field_positions
my %positions = $p->field_positions;
Returns a hash of the fields and their positions bound via
"bind_fields" (or "bind_header"). Mostly for internal use.
field_separator
$p->field_separator("\t"); # splits fields on tabs
$p->field_separator('::'); # splits fields on double colons
$p->field_separator(qr/\s+/); # splits fields on whitespace
my $sep = $p->field_separator; # returns the current separator
Gets and sets the token to use as the field delimiter. Regular
expressions can be specified using qr//. If not specified, it will
take a guess based on the filename extension ("comma" for ".txt,"
".dat," or ".csv"; "tab" for ".tab"). The default is a comma.
filename
$p->filename('/path/to/file.dat');
Gets or sets the complete path to the file to be read. If a file is
already opened, then the handle on it will be closed and a new one
opened on the new file.
get_field_aliases
my @aliases = $p->get_field_aliases('name');
Allows you to define alternate names for fields, e.g., sometimes your
input file calls city "town" or "township," sometimes a file uses
"Moniker" instead of "name."
header_filter
$p->header_filter( sub { $_ = shift; s/\s+/_/g; lc $_ } );
A callback applied to column header names. The callback will be passed
the current value of the header. Whatever is returned will become the
new value of the header. The above example collapses spaces into a
single underscore and lowercases the letters. To unset a filter, pass
in the empty string.
record_separator
$p->record_separator("\n//\n");
$p->field_separator("\n");
Gets and sets the token to use as the record separator. The default is
a newline ("\n").
The above example would read a file that looks like this:
field1
field2
field3
//
data1
data2
data3
//
set_field_alias
$p->set_field_alias({
name => 'Moniker,handle', # comma-separated string
city => [ qw( town township ) ], # or anonymous arrayref
});
Allows you to define alternate names for fields, e.g., sometimes your
input file calls city "town" or "township," sometimes a file uses
"Moniker" instead of "name."
trim
my $trim_value = $p->trim(1);
Provide "true" argument to remove leading and trailing whitespace from
fields. Use a "false" argument to disable.
AUTHOR
Ken Youens-Clark <kclark@cpan.org>
CREDITS
Thanks to the following:
· Benjamin Tilly
For Text::xSV, the inspirado for this module
· Tim Bunce et al.
For DBI, from which many of the methods were shamelessly stolen
· Tom Aldcroft
For contributing code to make it easy to parse whitespace-delimited
data
· Liya Ren
For catching the column-ordering error when parsing with "no-
headers"
· Sharon Wei
For catching bug in "extract" that sets up infinite loops
· Lars Thegler
For bug report on missing "script_files" arg in Build.PL
BUGS
None known. Please use http://rt.cpan.org/ for reporting bugs.
LICENSE AND COPYRIGHT
Copyright (C) 2006-10 Ken Youens-Clark. All rights reserved.
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; version 2.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
perl v5.14.2 2012-01-14 Text::RecordParser(3)
