Class: CSV

Inherits:
Object
  • Object
show all
Extended by:
Forwardable
Includes:
Enumerable
Defined in:
lib/csv.rb,
lib/csv/row.rb,
lib/csv/table.rb,
lib/csv/parser.rb,
lib/csv/writer.rb,
lib/csv/match_p.rb,
lib/csv/version.rb,
lib/csv/delete_suffix.rb,
lib/csv/fields_converter.rb

Overview

This class provides a complete interface to CSV files and data. It offers tools to enable you to read and write to and from Strings or IO objects, as needed.

The most generic interface of the library is:

csv = CSV.new(string_or_io, **options)

# Reading: IO object should be open for read
csv.read # => array of rows
# or
csv.each do |row|
  # ...
end
# or
row = csv.shift

# Writing: IO object should be open for write
csv << row

There are several specialized class methods for one-statement reading or writing, described in the Specialized Methods section.

If a String is passed into ::new, it is internally wrapped into a StringIO object.

options can be used for specifying the particular CSV flavor (column separators, row separators, value quoting and so on), and for data conversion, see Data Conversion section for the description of the latter.

Specialized Methods

Reading

# From a file: all at once
arr_of_rows = CSV.read("path/to/file.csv", **options)
# iterator-style:
CSV.foreach("path/to/file.csv", **options) do |row|
  # ...
end

# From a string
arr_of_rows = CSV.parse("CSV,data,String", **options)
# or
CSV.parse("CSV,data,String", **options) do |row|
  # ...
end

Writing

# To a file
CSV.open("path/to/file.csv", "wb") do |csv|
  csv << ["row", "of", "CSV", "data"]
  csv << ["another", "row"]
  # ...
end

# To a String
csv_string = CSV.generate do |csv|
  csv << ["row", "of", "CSV", "data"]
  csv << ["another", "row"]
  # ...
end

Shortcuts

# Core extensions for converting one line
csv_string = ["CSV", "data"].to_csv   # to CSV
csv_array  = "CSV,String".parse_csv   # from CSV

# CSV() method
CSV             { |csv_out| csv_out << %w{my data here} }  # to $stdout
CSV(csv = "")   { |csv_str| csv_str << %w{my data here} }  # to a String
CSV($stderr)    { |csv_err| csv_err << %w{my data here} }  # to $stderr
CSV($stdin)     { |csv_in|  csv_in.each { |row| p row } }  # from $stdin

Options

The default values for options are:

DEFAULT_OPTIONS = {
  # For both parsing and generating.
  col_sep:            ",",
  row_sep:            :auto,
  quote_char:         '"',
  # For parsing.
  field_size_limit:   nil,
  converters:         nil,
  unconverted_fields: nil,
  headers:            false,
  return_headers:     false,
  header_converters:  nil,
  skip_blanks:        false,
  skip_lines:         nil,
  liberal_parsing:    false,
  nil_value:          nil,
  empty_value:        "",
  # For generating.
  write_headers:      nil,
  quote_empty:        true,
  force_quotes:       false,
  write_converters:   nil,
  write_nil_value:    nil,
  write_empty_value:  "",
  strip:              false,
}

Options for Parsing

:include: ../doc/col_sep.rdoc

:include: ../doc/row_sep.rdoc

:include: ../doc/quote_char.rdoc

:include: ../doc/field_size_limit.rdoc

:include: ../doc/converters.rdoc

:include: ../doc/unconverted_fields.rdoc

:include: ../doc/headers.rdoc

:include: ../doc/return_headers.rdoc

:include: ../doc/header_converters.rdoc

:include: ../doc/skip_blanks.rdoc

:include: ../doc/skip_lines.rdoc

:include: ../doc/liberal_parsing.rdoc

:include: ../doc/nil_value.rdoc

:include: ../doc/empty_value.rdoc

Options for Generating

:include: ../doc/col_sep.rdoc

:include: ../doc/row_sep.rdoc

:include: ../doc/quote_char.rdoc

:include: ../doc/write_headers.rdoc

:include: ../doc/force_quotes.rdoc

:include: ../doc/quote_empty.rdoc

:include: ../doc/write_converters.rdoc

:include: ../doc/write_nil_value.rdoc

:include: ../doc/write_empty_value.rdoc

:include: ../doc/strip.rdoc

CSV with headers

CSV allows to specify column names of CSV file, whether they are in data, or provided separately. If headers are specified, reading methods return an instance of CSV::Table, consisting of CSV::Row.

# Headers are part of data
data = CSV.parse(<<~ROWS, headers: true)
  Name,Department,Salary
  Bob,Engineering,1000
  Jane,Sales,2000
  John,Management,5000
ROWS

data.class      #=> CSV::Table
data.first      #=> #<CSV::Row "Name":"Bob" "Department":"Engineering" "Salary":"1000">
data.first.to_h #=> {"Name"=>"Bob", "Department"=>"Engineering", "Salary"=>"1000"}

# Headers provided by developer
data = CSV.parse('Bob,Engineering,1000', headers: %i[name department salary])
data.first      #=> #<CSV::Row name:"Bob" department:"Engineering" salary:"1000">

CSV Converters

By default, each field parsed by CSV is formed into a String. You can use a converter to convert certain fields into other Ruby objects.

When you specify a converter for parsing, each parsed field is passed to the converter; its return value becomes the new value for the field. A converter might, for example, convert an integer embedded in a String into a true Integer. (In fact, that’s what built-in field converter :integer does.)

There are additional built-in converters, and custom converters are also supported.

All converters try to transcode fields to UTF-8 before converting. The conversion will fail if the data cannot be transcoded, leaving the field unchanged.

Field Converters

There are three ways to use field converters; these examples use built-in field converter :integer, which converts each parsed integer string to a true Integer.

Option converters with a singleton parsing method:

ary = CSV.parse_line('0,1,2', converters: :integer)
ary # => [0, 1, 2]

Option converters with a new CSV instance:

csv = CSV.new('0,1,2', converters: :integer)
# Field converters in effect:
csv.converters # => [:integer]
csv.shift # => [0, 1, 2]

Method #convert adds a field converter to a CSV instance:

csv = CSV.new('0,1,2')
# Add a converter.
csv.convert(:integer)
csv.converters # => [:integer]
csv.shift # => [0, 1, 2]

The built-in field converters are in Hash CSV::Converters. The Symbol keys there are the names of the converters:

CSV::Converters.keys # => [:integer, :float, :numeric, :date, :date_time, :all]

Converter :integer converts each field that Integer() accepts:

data = '0,1,2,x'
# Without the converter
csv = CSV.parse_line(data)
csv # => ["0", "1", "2", "x"]
# With the converter
csv = CSV.parse_line(data, converters: :integer)
csv # => [0, 1, 2, "x"]

Converter :float converts each field that Float() accepts:

data = '1.0,3.14159,x'
# Without the converter
csv = CSV.parse_line(data)
csv # => ["1.0", "3.14159", "x"]
# With the converter
csv = CSV.parse_line(data, converters: :float)
csv # => [1.0, 3.14159, "x"]

Converter :numeric converts with both :integer and :float..

Converter :date converts each field that Date::parse() accepts:

data = '2001-02-03,x'
# Without the converter
csv = CSV.parse_line(data)
csv # => ["2001-02-03", "x"]
# With the converter
csv = CSV.parse_line(data, converters: :date)
csv # => [#<Date: 2001-02-03 ((2451944j,0s,0n),+0s,2299161j)>, "x"]

Converter :date_time converts each field that +DateTime::parse() accepts:

data = '2020-05-07T14:59:00-05:00,x'
# Without the converter
csv = CSV.parse_line(data)
csv # => ["2020-05-07T14:59:00-05:00", "x"]
# With the converter
csv = CSV.parse_line(data, converters: :date_time)
csv # => [#<DateTime: 2020-05-07T14:59:00-05:00 ((2458977j,71940s,0n),-18000s,2299161j)>, "x"]

Converter :numeric converts with both :date_time and :numeric..

As seen above, method #convert adds converters to a CSV instance, and method #converters returns an Array of the converters in effect:

csv = CSV.new('0,1,2')
csv.converters # => []
csv.convert(:integer)
csv.converters # => [:integer]
csv.convert(:date)
csv.converters # => [:integer, :date]

You can add a custom field converter to Hash CSV::Converters:

strip_converter = proc {|field| field.strip}
CSV::Converters[:strip] = strip_converter
CSV::Converters.keys # => [:integer, :float, :numeric, :date, :date_time, :all, :strip]

Then use it to convert fields:

str = ' foo , 0 '
ary = CSV.parse_line(str, converters: :strip)
ary # => ["foo", "0"]

See Custom Converters.

Header Converters

Header converters operate only on headers (and not on other rows).

There are three ways to use header converters; these examples use built-in header converter :dowhcase, which downcases each parsed header.

Option header_converters with a singleton parsing method:

str = "Name,Count\nFoo,0\n,Bar,1\nBaz,2"
tbl = CSV.parse(str, headers: true, header_converters: :downcase)
tbl.class # => CSV::Table
tbl.headers # => ["name", "count"]

Option header_converters with a new CSV instance:

csv = CSV.new(str, header_converters: :downcase)
# Header converters in effect:
csv.header_converters # => [:downcase]
tbl = CSV.parse(str, headers: true)
tbl.headers # => ["Name", "Count"]

Method #header_convert adds a header converter to a CSV instance:

csv = CSV.new(str)
# Add a header converter.
csv.header_convert(:downcase)
csv.header_converters # => [:downcase]
tbl = CSV.parse(str, headers: true)
tbl.headers # => ["Name", "Count"]

The built-in header converters are in Hash CSV::Converters. The Symbol keys there are the names of the converters:

CSV::HeaderConverters.keys # => [:downcase, :symbol]

Converter :downcase converts each header by downcasing it:

str = "Name,Count\nFoo,0\n,Bar,1\nBaz,2"
tbl = CSV.parse(str, headers: true, header_converters: :downcase)
tbl.class # => CSV::Table
tbl.headers # => ["name", "count"]

Converter :symbol by making it into a Symbol:

str = "Name,Count\nFoo,0\n,Bar,1\nBaz,2"
tbl = CSV.parse(str, headers: true, header_converters: :symbol)
tbl.headers # => [:name, :count]

Details:

  • Strips leading and trailing whitespace.

  • Downcases the header.

  • Replaces embedded spaces with underscores.

  • Removes non-word characters.

  • Makes the string into a Symbol.

You can add a custom header converter to Hash CSV::HeaderConverters:

strip_converter = proc {|field| field.strip}
CSV::HeaderConverters[:strip] = strip_converter
CSV::HeaderConverters.keys # => [:downcase, :symbol, :strip]

Then use it to convert headers:

str = " Name , Value \nfoo,0\nbar,1\nbaz,2"
tbl = CSV.parse(str, headers: true, header_converters: :strip)
tbl.headers # => ["Name", "Value"]

See Custom Converters.

Custom Converters

You can define custom converters.

The converter is a Proc that is called with two arguments, String field and CSV::FieldInfo field_info; it returns a String that will become the field value:

converter = proc {|field, field_info| <some_string> }

To illustrate:

converter = proc {|field, field_info| p [field, field_info]; field}
ary = CSV.parse_line('foo,0', converters: converter)

Produces:

["foo", #<struct CSV::FieldInfo index=0, line=1, header=nil>]
["0", #<struct CSV::FieldInfo index=1, line=1, header=nil>]

In each of the output lines:

  • The first Array element is the passed String field.

  • The second is a FieldInfo structure containing information about the field:

    • The 0-based column index.

    • The 1-based line number.

    • The header for the column, if available.

If the converter does not need field_info, it can be omitted:

converter = proc {|field| ... }

CSV and Character Encodings (M17n or Multilingualization)

This new CSV parser is m17n savvy. The parser works in the Encoding of the IO or String object being read from or written to. Your data is never transcoded (unless you ask Ruby to transcode it for you) and will literally be parsed in the Encoding it is in. Thus CSV will return Arrays or Rows of Strings in the Encoding of your data. This is accomplished by transcoding the parser itself into your Encoding.

Some transcoding must take place, of course, to accomplish this multiencoding support. For example, :col_sep, :row_sep, and :quote_char must be transcoded to match your data. Hopefully this makes the entire process feel transparent, since CSV’s defaults should just magically work for your data. However, you can set these values manually in the target Encoding to avoid the translation.

It’s also important to note that while all of CSV’s core parser is now Encoding agnostic, some features are not. For example, the built-in converters will try to transcode data to UTF-8 before making conversions. Again, you can provide custom converters that are aware of your Encodings to avoid this translation. It’s just too hard for me to support native conversions in all of Ruby’s Encodings.

Anyway, the practical side of this is simple: make sure IO and String objects passed into CSV have the proper Encoding set and everything should just work. CSV methods that allow you to open IO objects (CSV::foreach(), CSV::open(), CSV::read(), and CSV::readlines()) do allow you to specify the Encoding.

One minor exception comes when generating CSV into a String with an Encoding that is not ASCII compatible. There’s no existing data for CSV to use to prepare itself and thus you will probably need to manually specify the desired Encoding for most of those cases. It will try to guess using the fields in a row of output though, when using CSV::generate_line() or Array#to_csv().

I try to point out any other Encoding issues in the documentation of methods as they come up.

This has been tested to the best of my ability with all non-“dummy” Encodings Ruby ships with. However, it is brave new code and may have some bugs. Please feel free to report any issues you find with it.

Defined Under Namespace

Modules: DeleteSuffix, MatchP Classes: FieldInfo, FieldsConverter, MalformedCSVError, Parser, Row, Table, Writer

Constant Summary collapse

DateMatcher =

A Regexp used to find and convert some common Date formats.

/ \A(?: (\w+,?\s+)?\w+\s+\d{1,2},?\s+\d{2,4} |
\d{4}-\d{2}-\d{2} )\z /x
DateTimeMatcher =

A Regexp used to find and convert some common DateTime formats.

/ \A(?: (\w+,?\s+)?\w+\s+\d{1,2}\s+\d{1,2}:\d{1,2}:\d{1,2},?\s+\d{2,4} |
    \d{4}-\d{2}-\d{2}\s\d{2}:\d{2}:\d{2} |
    # ISO-8601
    \d{4}-\d{2}-\d{2}
      (?:T\d{2}:\d{2}(?::\d{2}(?:\.\d+)?(?:[+-]\d{2}(?::\d{2})|Z)?)?)?
)\z /x
ConverterEncoding =

The encoding used by all converters.

Encoding.find("UTF-8")
Converters =

This Hash holds the built-in converters of CSV that can be accessed by name. You can select Converters with CSV.convert() or through the options Hash passed to CSV::new().

:integer

Converts any field Integer() accepts.

:float

Converts any field Float() accepts.

:numeric

A combination of :integer and :float.

:date

Converts any field Date::parse() accepts.

:date_time

Converts any field DateTime::parse() accepts.

:all

All built-in converters. A combination of :date_time and :numeric.

All built-in converters transcode field data to UTF-8 before attempting a conversion. If your data cannot be transcoded to UTF-8 the conversion will fail and the field will remain unchanged.

This Hash is intentionally left unfrozen and users should feel free to add values to it that can be accessed by all CSV objects.

To add a combo field, the value should be an Array of names. Combo fields can be nested with other combo fields.

{
  integer:   lambda { |f|
    Integer(f.encode(ConverterEncoding)) rescue f
  },
  float:     lambda { |f|
    Float(f.encode(ConverterEncoding)) rescue f
  },
  numeric:   [:integer, :float],
  date:      lambda { |f|
    begin
      e = f.encode(ConverterEncoding)
      e.match?(DateMatcher) ? Date.parse(e) : f
    rescue  # encoding conversion or date parse errors
      f
    end
  },
  date_time: lambda { |f|
    begin
      e = f.encode(ConverterEncoding)
      e.match?(DateTimeMatcher) ? DateTime.parse(e) : f
    rescue  # encoding conversion or date parse errors
      f
    end
  },
  all:       [:date_time, :numeric],
}
HeaderConverters =

This Hash holds the built-in header converters of CSV that can be accessed by name. You can select HeaderConverters with CSV.header_convert() or through the options Hash passed to CSV::new().

:downcase

Calls downcase() on the header String.

:symbol

Leading/trailing spaces are dropped, string is downcased, remaining spaces are replaced with underscores, non-word characters are dropped, and finally to_sym() is called.

All built-in header converters transcode header data to UTF-8 before attempting a conversion. If your data cannot be transcoded to UTF-8 the conversion will fail and the header will remain unchanged.

This Hash is intentionally left unfrozen and users should feel free to add values to it that can be accessed by all CSV objects.

To add a combo field, the value should be an Array of names. Combo fields can be nested with other combo fields.

{
  downcase: lambda { |h| h.encode(ConverterEncoding).downcase },
  symbol:   lambda { |h|
    h.encode(ConverterEncoding).downcase.gsub(/[^\s\w]+/, "").strip.
                                         gsub(/\s+/, "_").to_sym
  }
}
DEFAULT_OPTIONS =

Default values for method options.

{
  # For both parsing and generating.
  col_sep:            ",",
  row_sep:            :auto,
  quote_char:         '"',
  # For parsing.
  field_size_limit:   nil,
  converters:         nil,
  unconverted_fields: nil,
  headers:            false,
  return_headers:     false,
  header_converters:  nil,
  skip_blanks:        false,
  skip_lines:         nil,
  liberal_parsing:    false,
  nil_value:          nil,
  empty_value:        "",
  # For generating.
  write_headers:      nil,
  quote_empty:        true,
  force_quotes:       false,
  write_converters:   nil,
  write_nil_value:    nil,
  write_empty_value:  "",
  strip:              false,
}.freeze
VERSION =

The version of the installed library.

"3.1.4"

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(data, col_sep: ",", row_sep: :auto, quote_char: '"', field_size_limit: nil, converters: nil, unconverted_fields: nil, headers: false, return_headers: false, write_headers: nil, header_converters: nil, skip_blanks: false, force_quotes: false, skip_lines: nil, liberal_parsing: false, internal_encoding: nil, external_encoding: nil, encoding: nil, nil_value: nil, empty_value: "", quote_empty: true, write_converters: nil, write_nil_value: nil, write_empty_value: "", strip: false) ⇒ CSV

This constructor will wrap either a String or IO object passed in data for reading and/or writing. In addition to the CSV instance methods, several IO methods are delegated. (See CSV::open() for a complete list.) If you pass a String for data, you can later retrieve it (after writing to it, for example) with CSV.string().

Note that a wrapped String will be positioned at the beginning (for reading). If you want it at the end (for writing), use CSV::generate(). If you want any other positioning, pass a preset StringIO object instead.

See Options for Parsing and Options for Generating.

Options cannot be overridden in the instance methods for performance reasons, so be sure to set what you want here.

Raises:

  • (ArgumentError) 


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# File 'lib/csv.rb', line 1028

def initialize(data,
               col_sep: ",",
               row_sep: :auto,
               quote_char: '"',
               field_size_limit: nil,
               converters: nil,
               unconverted_fields: nil,
               headers: false,
               return_headers: false,
               write_headers: nil,
               header_converters: nil,
               skip_blanks: false,
               force_quotes: false,
               skip_lines: nil,
               liberal_parsing: false,
               internal_encoding: nil,
               external_encoding: nil,
               encoding: nil,
               nil_value: nil,
               empty_value: "",
               quote_empty: true,
               write_converters: nil,
               write_nil_value: nil,
               write_empty_value: "",
               strip: false)
  raise ArgumentError.new("Cannot parse nil as CSV") if data.nil?

  if data.is_a?(String)
    @io = StringIO.new(data)
    @io.set_encoding(encoding || data.encoding)
  else
    @io = data
  end
  @encoding = determine_encoding(encoding, internal_encoding)

  @base_fields_converter_options = {
    nil_value: nil_value,
    empty_value: empty_value,
  }
  @write_fields_converter_options = {
    nil_value: write_nil_value,
    empty_value: write_empty_value,
  }
  @initial_converters = converters
  @initial_header_converters = header_converters
  @initial_write_converters = write_converters

  @parser_options = {
    column_separator: col_sep,
    row_separator: row_sep,
    quote_character: quote_char,
    field_size_limit: field_size_limit,
    unconverted_fields: unconverted_fields,
    headers: headers,
    return_headers: return_headers,
    skip_blanks: skip_blanks,
    skip_lines: skip_lines,
    liberal_parsing: liberal_parsing,
    encoding: @encoding,
    nil_value: nil_value,
    empty_value: empty_value,
    strip: strip,
  }
  @parser = nil
  @parser_enumerator = nil
  @eof_error = nil

  @writer_options = {
    encoding: @encoding,
    force_encoding: (not encoding.nil?),
    force_quotes: force_quotes,
    headers: headers,
    write_headers: write_headers,
    column_separator: col_sep,
    row_separator: row_sep,
    quote_character: quote_char,
    quote_empty: quote_empty,
  }

  @writer = nil
  writer if @writer_options[:write_headers]
end

Instance Attribute Details

#encoding ⇒ Object (readonly)

The Encoding CSV is parsing or writing in. This will be the Encoding you receive parsed data in and/or the Encoding data will be written in.



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# File 'lib/csv.rb', line 1237

def encoding
  @encoding
end

Class Method Details

.filter(input = nil, output = nil, **options) ⇒ Object

:call-seq:

filter( **options ) { |row| ... }
filter( input, **options ) { |row| ... }
filter( input, output, **options ) { |row| ... }

This method is a convenience for building Unix-like filters for CSV data. Each row is yielded to the provided block which can alter it as needed. After the block returns, the row is appended to output altered or not.

The input and output arguments can be anything CSV::new() accepts (generally String or IO objects). If not given, they default to ARGF and $stdout.

The options parameter is also filtered down to CSV::new() after some clever key parsing. Any key beginning with :in_ or :input_ will have that leading identifier stripped and will only be used in the options Hash for the input object. Keys starting with :out_ or :output_ affect only output. All other keys are assigned to both objects.

See Options for Parsing and Options for Generating.

The :output_row_sep option defaults to $INPUT_RECORD_SEPARATOR ($/).



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# File 'lib/csv.rb', line 729

def filter(input=nil, output=nil, **options)
  # parse options for input, output, or both
  in_options, out_options = Hash.new, {row_sep: $INPUT_RECORD_SEPARATOR}
  options.each do |key, value|
    case key.to_s
    when /\Ain(?:put)?_(.+)\Z/
      in_options[$1.to_sym] = value
    when /\Aout(?:put)?_(.+)\Z/
      out_options[$1.to_sym] = value
    else
      in_options[key]  = value
      out_options[key] = value
    end
  end
  # build input and output wrappers
  input  = new(input  || ARGF,    **in_options)
  output = new(output || $stdout, **out_options)

  # read, yield, write
  input.each do |row|
    yield row
    output << row
  end
end

.foreach(path, mode = "r", **options, &block) ⇒ Object

This method is intended as the primary interface for reading CSV files. You pass a path and any options you wish to set for the read. Each row of file will be passed to the provided block in turn.

See Options for Parsing.

The options parameter can be anything CSV::new() understands. This method also understands an additional :encoding parameter that you can use to specify the Encoding of the data in the file to be read. You must provide this unless your data is in Encoding::default_external(). CSV will use this to determine how to parse the data. You may provide a second Encoding to have the data transcoded as it is read. For example, encoding: "UTF-32BE:UTF-8" would read UTF-32BE data from the file but transcode it to UTF-8 before CSV parses it.



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# File 'lib/csv.rb', line 770

def foreach(path, mode="r", **options, &block)
  return to_enum(__method__, path, mode, **options) unless block_given?
  open(path, mode, **options) do |csv|
    csv.each(&block)
  end
end

.generate(str = nil, **options) {|csv| ... } ⇒ Object

:call-seq:

generate( str, **options ) { |csv| ... }
generate( **options ) { |csv| ... }

This method wraps a String you provide, or an empty default String, in a CSV object which is passed to the provided block. You can use the block to append CSV rows to the String and when the block exits, the final String will be returned.

Note that a passed String is modified by this method. Call dup() before passing if you need a new String.

See Options for Generating.

This method has one additional option: :encoding, which sets the base Encoding for the output if no no str is specified. CSV needs this hint if you plan to output non-ASCII compatible data.

Yields:

  • (csv) 


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# File 'lib/csv.rb', line 796

def generate(str=nil, **options)
  encoding = options[:encoding]
  # add a default empty String, if none was given
  if str
    str = StringIO.new(str)
    str.seek(0, IO::SEEK_END)
    str.set_encoding(encoding) if encoding
  else
    str = +""
    str.force_encoding(encoding) if encoding
  end
  csv = new(str, **options) # wrap
  yield csv         # yield for appending
  csv.string        # return final String
end

.generate_line(row, **options) ⇒ Object

This method is a shortcut for converting a single row (Array) into a CSV String.

See Options for Generating.

This method accepts an additional option, :encoding, which sets the base Encoding for the output. This method will try to guess your Encoding from the first non-nil field in row, if possible, but you may need to use this parameter as a backup plan.

The :row_sep option defaults to $INPUT_RECORD_SEPARATOR ($/) when calling this method.



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# File 'lib/csv.rb', line 826

def generate_line(row, **options)
  options = {row_sep: $INPUT_RECORD_SEPARATOR}.merge(options)
  str = +""
  if options[:encoding]
    str.force_encoding(options[:encoding])
  elsif field = row.find {|f| f.is_a?(String)}
    str.force_encoding(field.encoding)
  end
  (new(str, **options) << row).string
end

.instance(data = $stdout, **options) ⇒ Object

This method will return a CSV instance, just like CSV::new(), but the instance will be cached and returned for all future calls to this method for the same data object (tested by Object#object_id()) with the same options.

See Options for Parsing and Options for Generating.

If a block is given, the instance is passed to the block and the return value becomes the return value of the block.



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# File 'lib/csv.rb', line 686

def instance(data = $stdout, **options)
  # create a _signature_ for this method call, data object and options
  sig = [data.object_id] +
        options.values_at(*DEFAULT_OPTIONS.keys.sort_by { |sym| sym.to_s })

  # fetch or create the instance for this signature
  @@instances ||= Hash.new
  instance = (@@instances[sig] ||= new(data, **options))

  if block_given?
    yield instance  # run block, if given, returning result
  else
    instance        # or return the instance
  end
end

.open(filename, mode = "r", **options) ⇒ Object

:call-seq:

open( filename, mode = "rb", **options ) { |faster_csv| ... }
open( filename, **options ) { |faster_csv| ... }
open( filename, mode = "rb", **options )
open( filename, **options )

This method opens an IO object, and wraps that with CSV. This is intended as the primary interface for writing a CSV file.

You must pass a filename and may optionally add a mode for Ruby’s open().

See Options for Generating.

This method works like Ruby’s open() call, in that it will pass a CSV object to a provided block and close it when the block terminates, or it will return the CSV object when no block is provided. (Note: This is different from the Ruby 1.8 CSV library which passed rows to the block. Use CSV::foreach() for that behavior.)

You must provide a mode with an embedded Encoding designator unless your data is in Encoding::default_external(). CSV will check the Encoding of the underlying IO object (set by the mode you pass) to determine how to parse the data. You may provide a second Encoding to have the data transcoded as it is read just as you can with a normal call to IO::open(). For example, "rb:UTF-32BE:UTF-8" would read UTF-32BE data from the file but transcode it to UTF-8 before CSV parses it.

An opened CSV object will delegate to many IO methods for convenience. You may call:

  • binmode()

  • binmode?()

  • close()

  • close_read()

  • close_write()

  • closed?()

  • eof()

  • eof?()

  • external_encoding()

  • fcntl()

  • fileno()

  • flock()

  • flush()

  • fsync()

  • internal_encoding()

  • ioctl()

  • isatty()

  • path()

  • pid()

  • pos()

  • pos=()

  • reopen()

  • seek()

  • stat()

  • sync()

  • sync=()

  • tell()

  • to_i()

  • to_io()

  • truncate()

  • tty?()



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# File 'lib/csv.rb', line 901

def open(filename, mode="r", **options)
  # wrap a File opened with the remaining +args+ with no newline
  # decorator
  file_opts = {universal_newline: false}.merge(options)

  begin
    f = File.open(filename, mode, **file_opts)
  rescue ArgumentError => e
    raise unless /needs binmode/.match?(e.message) and mode == "r"
    mode = "rb"
    file_opts = {encoding: Encoding.default_external}.merge(file_opts)
    retry
  end
  begin
    csv = new(f, **options)
  rescue Exception
    f.close
    raise
  end

  # handle blocks like Ruby's open(), not like the CSV library
  if block_given?
    begin
      yield csv
    ensure
      csv.close
    end
  else
    csv
  end
end

.parse(str, **options, &block) ⇒ Object

:call-seq:

parse( str, **options ) { |row| ... }
parse( str, **options )

This method can be used to easily parse CSV out of a String. You may either provide a block which will be called with each row of the String in turn, or just use the returned Array of Arrays (when no block is given).

You pass your str to read from, and an optional options. See Options for Parsing.



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# File 'lib/csv.rb', line 945

def parse(str, **options, &block)
  csv = new(str, **options)

  return csv.each(&block) if block_given?

  # slurp contents, if no block is given
  begin
    csv.read
  ensure
    csv.close
  end
end

.parse_line(line, **options) ⇒ Object

This method is a shortcut for converting a single line of a CSV String into an Array. Note that if line contains multiple rows, anything beyond the first row is ignored.

See Options for Parsing.



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# File 'lib/csv.rb', line 965

def parse_line(line, **options)
  new(line, **options).each.first
end

.read(path, **options) ⇒ Object

Use to slurp a CSV file into an Array of Arrays. Pass the path to the file and options. See Options for Parsing.

This method also understands an additional :encoding parameter that you can use to specify the Encoding of the data in the file to be read. You must provide this unless your data is in Encoding::default_external(). CSV will use this to determine how to parse the data. You may provide a second Encoding to have the data transcoded as it is read. For example, encoding: "UTF-32BE:UTF-8" would read UTF-32BE data from the file but transcode it to UTF-8 before CSV parses it.



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# File 'lib/csv.rb', line 983

def read(path, **options)
  open(path, **options) { |csv| csv.read }
end

.readlines(path, **options) ⇒ Object

Alias for CSV::read().



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# File 'lib/csv.rb', line 988

def readlines(path, **options)
  read(path, **options)
end

.table(path, **options) ⇒ Object

A shortcut for:

CSV.read( path, { headers:           true,
                  converters:        :numeric,
                  header_converters: :symbol }.merge(options) )

See Options for Parsing.



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# File 'lib/csv.rb', line 1000

def table(path, **options)
  default_options = {
    headers:           true,
    converters:        :numeric,
    header_converters: :symbol,
  }
  options = default_options.merge(options)
  read(path, **options)
end

Instance Method Details

#<<(row) ⇒ Object Also known as: add_row, puts

The primary write method for wrapped Strings and IOs, row (an Array or CSV::Row) is converted to CSV and appended to the data source. When a CSV::Row is passed, only the row’s fields() are appended to the output.

The data source must be open for writing.



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# File 'lib/csv.rb', line 1336

def <<(row)
  writer << row
  self
end

#binmode? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/csv.rb', line 1268

def binmode?
  if @io.respond_to?(:binmode?)
    @io.binmode?
  else
    false
  end
end

#col_sep ⇒ Object

The encoded :col_sep used in parsing and writing. See CSV::new for details.



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# File 'lib/csv.rb', line 1115

def col_sep
  parser.column_separator
end

#convert(name = nil, &converter) ⇒ Object

:call-seq:

convert( name )
convert { |field| ... }
convert { |field, field_info| ... }

You can use this method to install a CSV::Converters built-in, or provide a block that handles a custom conversion.

If you provide a block that takes one argument, it will be passed the field and is expected to return the converted value or the field itself. If your block takes two arguments, it will also be passed a CSV::FieldInfo Struct, containing details about the field. Again, the block should return a converted field or the field itself.



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# File 'lib/csv.rb', line 1358

def convert(name = nil, &converter)
  parser_fields_converter.add_converter(name, &converter)
end

#converters ⇒ Object

Returns the current list of converters in effect. See CSV::new for details. Built-in converters will be returned by name, while others will be returned as is.



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# File 'lib/csv.rb', line 1156

def converters
  parser_fields_converter.map do |converter|
    name = Converters.rassoc(converter)
    name ? name.first : converter
  end
end

#each(&block) ⇒ Object

Yields each row of the data source in turn.

Support for Enumerable.

The data source must be open for reading.



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# File 'lib/csv.rb', line 1386

def each(&block)
  parser_enumerator.each(&block)
end

#eof? ⇒ Boolean Also known as: eof

Returns:

  • (Boolean) 


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# File 'lib/csv.rb', line 1304

def eof?
  return false if @eof_error
  begin
    parser_enumerator.peek
    false
  rescue MalformedCSVError => error
    @eof_error = error
    false
  rescue StopIteration
    true
  end
end

#field_size_limit ⇒ Object

The limit for field size, if any. See CSV::new for details.



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# File 'lib/csv.rb', line 1139

def field_size_limit
  parser.field_size_limit
end

#flock(*args) ⇒ Object

Raises:

  • (NotImplementedError) 


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# File 'lib/csv.rb', line 1276

def flock(*args)
  raise NotImplementedError unless @io.respond_to?(:flock)
  @io.flock(*args)
end

#force_quotes? ⇒ Boolean

Returns true if all output fields are quoted. See CSV::new for details.

Returns:

  • (Boolean) 


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# File 'lib/csv.rb', line 1224

def force_quotes?
  @writer_options[:force_quotes]
end

#header_convert(name = nil, &converter) ⇒ Object

:call-seq:

header_convert( name )
header_convert { |field| ... }
header_convert { |field, field_info| ... }

Identical to CSV#convert(), but for header rows.

Note that this method must be called before header rows are read to have any effect.



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# File 'lib/csv.rb', line 1373

def header_convert(name = nil, &converter)
  header_fields_converter.add_converter(name, &converter)
end

#header_converters ⇒ Object

Returns the current list of converters in effect for headers. See CSV::new for details. Built-in converters will be returned by name, while others will be returned as is.



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# File 'lib/csv.rb', line 1208

def header_converters
  header_fields_converter.map do |converter|
    name = HeaderConverters.rassoc(converter)
    name ? name.first : converter
  end
end

#header_row? ⇒ Boolean

Returns true if the next row read will be a header row.

Returns:

  • (Boolean) 


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# File 'lib/csv.rb', line 1406

def header_row?
  parser.header_row?
end

#headers ⇒ Object

Returns nil if headers will not be used, true if they will but have not yet been read, or the actual headers after they have been read. See CSV::new for details.



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# File 'lib/csv.rb', line 1176

def headers
  if @writer
    @writer.headers
  else
    parsed_headers = parser.headers
    return parsed_headers if parsed_headers
    raw_headers = @parser_options[:headers]
    raw_headers = nil if raw_headers == false
    raw_headers
  end
end

#inspect ⇒ Object

Returns a simplified description of the key CSV attributes in an ASCII compatible String.



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# File 'lib/csv.rb', line 1435

def inspect
  str = ["#<", self.class.to_s, " io_type:"]
  # show type of wrapped IO
  if    @io == $stdout then str << "$stdout"
  elsif @io == $stdin  then str << "$stdin"
  elsif @io == $stderr then str << "$stderr"
  else                      str << @io.class.to_s
  end
  # show IO.path(), if available
  if @io.respond_to?(:path) and (p = @io.path)
    str << " io_path:" << p.inspect
  end
  # show encoding
  str << " encoding:" << @encoding.name
  # show other attributes
  ["lineno", "col_sep", "row_sep", "quote_char"].each do |attr_name|
    if a = __send__(attr_name)
      str << " " << attr_name << ":" << a.inspect
    end
  end
  ["skip_blanks", "liberal_parsing"].each do |attr_name|
    if a = __send__("#{attr_name}?")
      str << " " << attr_name << ":" << a.inspect
    end
  end
  _headers = headers
  str << " headers:" << _headers.inspect if _headers
  str << ">"
  begin
    str.join('')
  rescue  # any encoding error
    str.map do |s|
      e = Encoding::Converter.asciicompat_encoding(s.encoding)
      e ? s.encode(e) : s.force_encoding("ASCII-8BIT")
    end.join('')
  end
end

#ioctl(*args) ⇒ Object

Raises:

  • (NotImplementedError) 


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# File 'lib/csv.rb', line 1281

def ioctl(*args)
  raise NotImplementedError unless @io.respond_to?(:ioctl)
  @io.ioctl(*args)
end

#liberal_parsing? ⇒ Boolean

Returns true if illegal input is handled. See CSV::new for details.

Returns:

  • (Boolean) 


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# File 'lib/csv.rb', line 1229

def liberal_parsing?
  parser.liberal_parsing?
end

#line ⇒ Object

The last row read from this file.



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# File 'lib/csv.rb', line 1254

def line
  parser.line
end

#lineno ⇒ Object

The line number of the last row read from this file. Fields with nested line-end characters will not affect this count.



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# File 'lib/csv.rb', line 1243

def lineno
  if @writer
    @writer.lineno
  else
    parser.lineno
  end
end

#path ⇒ Object 



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# File 'lib/csv.rb', line 1286

def path
  @io.path if @io.respond_to?(:path)
end

#quote_char ⇒ Object

The encoded :quote_char used in parsing and writing. See CSV::new for details.



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# File 'lib/csv.rb', line 1131

def quote_char
  parser.quote_character
end

#read ⇒ Object Also known as: readlines

Slurps the remaining rows and returns an Array of Arrays.

The data source must be open for reading.



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# File 'lib/csv.rb', line 1395

def read
  rows = to_a
  if parser.use_headers?
    Table.new(rows, headers: parser.headers)
  else
    rows
  end
end

#return_headers? ⇒ Boolean

Returns true if headers will be returned as a row of results. See CSV::new for details.

Returns:

  • (Boolean) 


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# File 'lib/csv.rb', line 1191

def return_headers?
  parser.return_headers?
end

#rewind ⇒ Object

Rewinds the underlying IO object and resets CSV’s lineno() counter.



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# File 'lib/csv.rb', line 1319

def rewind
  @parser = nil
  @parser_enumerator = nil
  @eof_error = nil
  @writer.rewind if @writer
  @io.rewind
end

#row_sep ⇒ Object

The encoded :row_sep used in parsing and writing. See CSV::new for details.



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# File 'lib/csv.rb', line 1123

def row_sep
  parser.row_separator
end

#shift ⇒ Object Also known as: gets, readline

The primary read method for wrapped Strings and IOs, a single row is pulled from the data source, parsed and returned as an Array of fields (if header rows are not used) or a CSV::Row (when header rows are used).

The data source must be open for reading.



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# File 'lib/csv.rb', line 1417

def shift
  if @eof_error
    eof_error, @eof_error = @eof_error, nil
    raise eof_error
  end
  begin
    parser_enumerator.next
  rescue StopIteration
    nil
  end
end

#skip_blanks? ⇒ Boolean

Returns true blank lines are skipped by the parser. See CSV::new for details.

Returns:

  • (Boolean) 


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# File 'lib/csv.rb', line 1219

def skip_blanks?
  parser.skip_blanks?
end

#skip_lines ⇒ Object

The regex marking a line as a comment. See CSV::new for details.



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# File 'lib/csv.rb', line 1147

def skip_lines
  parser.skip_lines
end

#stat(*args) ⇒ Object

Raises:

  • (NotImplementedError) 


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# File 'lib/csv.rb', line 1290

def stat(*args)
  raise NotImplementedError unless @io.respond_to?(:stat)
  @io.stat(*args)
end

#to_i ⇒ Object

Raises:

  • (NotImplementedError) 


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# File 'lib/csv.rb', line 1295

def to_i
  raise NotImplementedError unless @io.respond_to?(:to_i)
  @io.to_i
end

#to_io ⇒ Object 



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# File 'lib/csv.rb', line 1300

def to_io
  @io.respond_to?(:to_io) ? @io.to_io : @io
end

#unconverted_fields? ⇒ Boolean

Returns true if unconverted_fields() to parsed results. See CSV::new for details.

Returns:

  • (Boolean) 


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# File 'lib/csv.rb', line 1167

def unconverted_fields?
  parser.unconverted_fields?
end

#write_headers? ⇒ Boolean

Returns true if headers are written in output. See CSV::new for details.

Returns:

  • (Boolean) 


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# File 'lib/csv.rb', line 1199

def write_headers?
  @writer_options[:write_headers]
end