Class: CSV

Relationships & Source Files
Namespace Children
Modules: `DeleteSuffix`, `MatchP`
Classes: `FieldInfo`, `FieldsConverter`, `Parser`, `Row`, `Table`, `Writer`
Exceptions: `MalformedCSVError`
Super Chains via Extension / Inclusion / Inheritance
Class Chain: self, Forwardable
Instance Chain: self, Enumerable
Inherits:	Object
Defined in:	lib/csv.rb, lib/csv/delete_suffix.rb, lib/csv/fields_converter.rb, lib/csv/match_p.rb, lib/csv/parser.rb, lib/csv/row.rb, lib/csv/table.rb, lib/csv/version.rb, lib/csv/writer.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

Data Conversion

CSV with headers

CSV allows to specify column names of CSV file, whether they are in data, or provided separately. If headers specified, reading methods return an instance of Table, consisting of 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,Engeneering,1000', headers: %i[name department salary])
data.first      #=> #<CSV::Row name:"Bob" department:"Engineering" salary:"1000">

Typed data reading

CSV allows to provide a set of data converters e.g. transformations to try on input data. Converter could be a symbol from Converters constant’s keys, or lambda.

# Without any converters:
CSV.parse('Bob,2018-03-01,100')
#=> [["Bob", "2018-03-01", "100"]]

# With built-in converters:
CSV.parse('Bob,2018-03-01,100', converters: %i[numeric date])
#=> [["Bob", #<Date: 2018-03-01>, 100]]

# With custom converters:
CSV.parse('Bob,2018-03-01,100', converters: [->(v) { Time.parse(v) rescue v }])
#=> [["Bob", 2018-03-01 00:00:00 +0200, "100"]]

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(), .open(), .read(), and .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 .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.

Constant Summary

ConverterEncoding =

The encoding used by all converters.

# File 'lib/csv.rb', line 302
```
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 #convert() or through the options Hash passed to .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.

# File 'lib/csv.rb', line 328
```
{
  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],
}
```

DEFAULT_OPTIONS =

The options used when no overrides are given by calling code. They are:

:col_sep: ","
:row_sep: :auto
:quote_char: '"'
:field_size_limit: nil
:converters: nil
:unconverted_fields: nil
:headers: false
:return_headers: false
:header_converters: nil
:skip_blanks: false
:force_quotes: false
:skip_lines: nil
:liberal_parsing: false
:quote_empty: true

# File 'lib/csv.rb', line 402

{
  col_sep:            ",",
  row_sep:            :auto,
  quote_char:         '"',
  field_size_limit:   nil,
  converters:         nil,
  unconverted_fields: nil,
  headers:            false,
  return_headers:     false,
  header_converters:  nil,
  skip_blanks:        false,
  force_quotes:       false,
  skip_lines:         nil,
  liberal_parsing:    false,
  quote_empty:        true,
}.freeze

DateMatcher =

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

# File 'lib/csv.rb', line 290
```
/ \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.

# File 'lib/csv.rb', line 293

/ \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

HeaderConverters =

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

# File 'lib/csv.rb', line 376
```
{
  downcase: lambda { |h| h.encode(ConverterEncoding).downcase },
  symbol:   lambda { |h|
    h.encode(ConverterEncoding).downcase.gsub(/[^\s\w]+/, "").strip.
                                         gsub(/\s+/, "_").to_sym
  }
}
```
VERSION =

The version of the installed library.

# File 'lib/csv/version.rb', line 5
```
"3.0.9"
```

Class Method Summary

.filter(**options) {|row| ... }

This method is a convenience for building Unix-like filters for CSV data.
.foreach(path, mode = "r", **options, &block)

This method is intended as the primary interface for reading CSV files.
.generate(str, **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.
.generate_line(row, **options)

This method is a shortcut for converting a single row (Array) into a CSV String.
.instance(data = $stdout, **options)

This method will return a CSV instance, just like .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.
.new(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 constructor

This constructor will wrap either a ::String or IO object passed in data for reading and/or writing.
.open(filename, mode = "rb", **options) {|faster_csv| ... }

This method opens an IO object, and wraps that with CSV.
.parse(str, **options) {|row| ... }

This method can be used to easily parse CSV out of a ::String.
.parse_line(line, **options)

This method is a shortcut for converting a single line of a CSV String into an ::Array.
.read(path, *options)

Use to slurp a CSV file into an ::Array of Arrays.
.readlines(*args)

Alias for .read().
.table(path, **options)

A shortcut for:

Instance Attribute Summary

#binmode? ⇒ Boolean readonly
#encoding readonly

The Encoding CSV is parsing or writing in.
#eof readonly

Alias for #eof?.
#force_quotes? ⇒ Boolean readonly

Returns true if all output fields are quoted.
#header_row? ⇒ Boolean readonly

Returns true if the next row read will be a header row.
#liberal_parsing? ⇒ Boolean readonly

Returns true if illegal input is handled.
#return_headers? ⇒ Boolean readonly

Returns true if headers will be returned as a row of results.
#skip_blanks? ⇒ Boolean readonly

Returns true blank lines are skipped by the parser.
#unconverted_fields? ⇒ Boolean readonly

Returns true if unconverted_fields() to parsed results.
#write_headers? ⇒ Boolean readonly

Returns true if headers are written in output.

Instance Method Summary

#<<(row) (also: #add_row, #puts)

The primary write method for wrapped Strings and IOs, row (an ::Array or Row) is converted to CSV and appended to the data source.
#add_row(row)

Alias for #<<.
#col_sep

The encoded :col_sep used in parsing and writing.
#convert(name)

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

Returns the current list of converters in effect.
#each(&block)

Yields each row of the data source in turn.
#eof? ⇒ Boolean (also: #eof) readonly
#field_size_limit

The limit for field size, if any.
#flock(*args)
#gets

Alias for #shift.
#header_convert(name)

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

Returns the current list of converters in effect for headers.
#headers

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.
#inspect

Returns a simplified description of the key CSV attributes in an ASCII compatible ::String.
#ioctl(*args)
#line

The last row read from this file.
#lineno

The line number of the last row read from this file.
#path
#puts(row)

Alias for #<<.
#quote_char

The encoded :quote_char used in parsing and writing.
#read (also: #readlines)

Slurps the remaining rows and returns an ::Array of Arrays.
#readline

Alias for #shift.
#readlines

Alias for #read.
#rewind

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

The encoded :row_sep used in parsing and writing.
#shift (also: #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 Row (when header rows are used).
#skip_lines

The regex marking a line as a comment.
#stat(*args)
#to_i
#to_io
#build_fields_converter(initial_converters, options) private
#build_header_fields_converter private
#build_parser_fields_converter private
#build_writer_fields_converter private
#convert_fields(fields, headers = false) private

Processes fields with @converters, or @header_converters if #headers is passed as true, returning the converted field set.
#determine_encoding(encoding, internal_encoding) private
#header_fields_converter private
#normalize_converters(converters) private
#parser private
#parser_enumerator private
#parser_fields_converter private
#parser_options private
#raw_encoding private

Returns the encoding of the internal IO object.
#writer private
#writer_fields_converter private
#writer_options private

Constructor Details

.new(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 .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 .generate(). If you want any other positioning, pass a preset StringIO object instead.

You may set any reading and/or writing preferences in the options Hash. Available options are:

:col_sep: The String placed between each field. This String will be transcoded into the data’s Encoding before parsing.
:row_sep: The String appended to the end of each row. This can be set to the special :auto setting, which requests that CSV automatically discover this from the data. Auto-discovery reads ahead in the data looking for the next "\r\n", "\n", or "\r" sequence. A sequence will be selected even if it occurs in a quoted field, assuming that you would have the same line endings there. If none of those sequences is found, data is ARGF, STDIN, STDOUT, or STDERR, or the stream is only available for output, the default $INPUT_RECORD_SEPARATOR ($/) is used. Obviously, discovery takes a little time. Set manually if speed is important. Also note that IO objects should be opened in binary mode on Windows if this feature will be used as the line-ending translation can cause problems with resetting the document position to where it was before the read ahead. This String will be transcoded into the data’s Encoding before parsing.
:quote_char: The character used to quote fields. This has to be a single character String. This is useful for application that incorrectly use ' as the quote character instead of the correct ". CSV will always consider a double sequence of this character to be an escaped quote. This String will be transcoded into the data’s Encoding before parsing.
:field_size_limit: This is a maximum size CSV will read ahead looking for the closing quote for a field. (In truth, it reads to the first line ending beyond this size.) If a quote cannot be found within the limit CSV will raise a MalformedCSVError, assuming the data is faulty. You can use this limit to prevent what are effectively DoS attacks on the parser. However, this limit can cause a legitimate parse to fail and thus is set to nil, or off, by default.
:converters: An Array of names from the Converters Hash and/or lambdas that handle custom conversion. A single converter doesn’t have to be in an Array. All built-in converters try to transcode fields to UTF-8 before converting. The conversion will fail if the data cannot be transcoded, leaving the field unchanged.
:unconverted_fields: If set to true, an unconverted_fields() method will be added to all returned rows (Array or CSV::Row) that will return the fields as they were before conversion. Note that :headers supplied by Array or String were not fields of the document and thus will have an empty Array attached.
:headers: If set to :first_row or true, the initial row of the CSV file will be treated as a row of headers. If set to an Array, the contents will be used as the headers. If set to a String, the String is run through a call of CSV::parse_line() with the same :col_sep, :row_sep, and :quote_char as this instance to produce an Array of headers. This setting causes CSV#shift() to return rows as CSV::Row objects instead of Arrays and CSV#read() to return CSV::Table objects instead of an Array of Arrays.
:return_headers: When false, header rows are silently swallowed. If set to true, header rows are returned in a CSV::Row object with identical headers and fields (save that the fields do not go through the converters).
:write_headers: When true and :headers is set, a header row will be added to the output.
:header_converters: Identical in functionality to :converters save that the conversions are only made to header rows. All built-in converters try to transcode headers to UTF-8 before converting. The conversion will fail if the data cannot be transcoded, leaving the header unchanged.
:skip_blanks: When set to a true value, CSV will skip over any empty rows. Note that this setting will not skip rows that contain column separators, even if the rows contain no actual data. If you want to skip rows that contain separators but no content, consider using :skip_lines, or inspecting fields.compact.empty? on each row.
:force_quotes: When set to a true value, CSV will quote all CSV fields it creates.
:skip_lines: When set to an object responding to match, every line matching it is considered a comment and ignored during parsing. When set to a String, it is first converted to a Regexp. When set to nil no line is considered a comment. If the passed object does not respond to match, ArgumentError is thrown.
:liberal_parsing: When set to a true value, CSV will attempt to parse input not conformant with RFC 4180, such as double quotes in unquoted fields.
:nil_value: When set an object, any values of an empty field are replaced by the set object, not nil.
:empty_value: When set an object, any values of a blank string field is replaced by the set object.
:quote_empty: TODO
:write_converters: TODO
:write_nil_value: TODO
:write_empty_value: TODO
:strip: TODO

See DEFAULT_OPTIONS for the default settings.

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

Raises:

(ArgumentError)

[ GitHub ]

# File 'lib/csv.rb', line 898


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?

  # create the IO object we will read from
  @io = data.is_a?(String) ? StringIO.new(data) : data
  @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

  @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

Class Method Details

.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 .new() accepts (generally ::String or IO objects). If not given, they default to ARGF and $stdout.

The options parameter is also filtered down to .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.

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

[ GitHub ]

# File 'lib/csv.rb', line 468


def self.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)

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.

The options parameter can be anything .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.

[ GitHub ]

# File 'lib/csv.rb', line 507


def self.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, 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.

The options parameter can be anything .new() understands. This method understands an additional :encoding parameter when not passed a ::String to set the base Encoding for the output. CSV needs this hint if you plan to output non-ASCII compatible data.

Yields:

(csv)

[ GitHub ]

# File 'lib/csv.rb', line 532


def self.generate(str=nil, **options)
  # add a default empty String, if none was given
  if str
    str = StringIO.new(str)
    str.seek(0, IO::SEEK_END)
  else
    encoding = options[:encoding]
    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)

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

The options parameter can be anything .new() understands. This method understands an additional :encoding parameter to set 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.

[ GitHub ]

# File 'lib/csv.rb', line 560


def self.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)

This method will return a CSV instance, just like .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.

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

[ GitHub ]

# File 'lib/csv.rb', line 428


def self.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 = "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(). You may also pass an optional Hash containing any options .new() understands as the final argument.

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 .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?()

[ GitHub ]

# File 'lib/csv.rb', line 634


def self.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) {|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 containing anything .new() understands.

[ GitHub ]

# File 'lib/csv.rb', line 678


def self.parse(*args, &block)
  csv = new(*args)

  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)

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.

The options parameter can be anything .new() understands.

[ GitHub ]

# File 'lib/csv.rb', line 698


def self.parse_line(line, **options)
  new(line, options).shift
end

.read(path, *options)

Use to slurp a CSV file into an ::Array of Arrays. Pass the #path to the file and any options .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.

[ GitHub ]

# File 'lib/csv.rb', line 713


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

.readlines(*args)

Alias for .read().

[ GitHub ]

# File 'lib/csv.rb', line 718


def self.readlines(*args)
  read(*args)
end

.table(path, **options)

A shortcut for:

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

[ GitHub ]

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


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

Instance Attribute Details

#binmode? ⇒ `Boolean` (readonly)

[ GitHub ]

# File 'lib/csv.rb', line 1122


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

#encoding (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.

[ GitHub ]

# File 'lib/csv.rb', line 1091


attr_reader :encoding

#eof (readonly)

Alias for #eof?.

[ GitHub ]

# File 'lib/csv.rb', line 1166


alias_method :eof, :eof?

#force_quotes? ⇒ `Boolean` (readonly)

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

[ GitHub ]

# File 'lib/csv.rb', line 1078


def force_quotes?
  @writer_options[:force_quotes]
end

#header_row? ⇒ `Boolean` (readonly)

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

[ GitHub ]

# File 'lib/csv.rb', line 1255


def header_row?
  parser.header_row?
end

#liberal_parsing? ⇒ `Boolean` (readonly)

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

[ GitHub ]

# File 'lib/csv.rb', line 1083


def liberal_parsing?
  parser.liberal_parsing?
end

#return_headers? ⇒ `Boolean` (readonly)

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

[ GitHub ]

# File 'lib/csv.rb', line 1048


def return_headers?
  parser.return_headers?
end

#skip_blanks? ⇒ `Boolean` (readonly)

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

[ GitHub ]

# File 'lib/csv.rb', line 1073


def skip_blanks?
  parser.skip_blanks?
end

#unconverted_fields? ⇒ `Boolean` (readonly)

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

[ GitHub ]

# File 'lib/csv.rb', line 1024


def unconverted_fields?
  parser.unconverted_fields?
end

#write_headers? ⇒ `Boolean` (readonly)

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

[ GitHub ]

# File 'lib/csv.rb', line 1053


def write_headers?
  @writer_options[:write_headers]
end

Instance Method Details

#<<(row) 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.

[ GitHub ]

# File 'lib/csv.rb', line 1185


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

#add_row(row)

Alias for #<<.

[ GitHub ]

# File 'lib/csv.rb', line 1189


alias_method :add_row, :<<

#build_fields_converter(initial_converters, options) (private)

[ GitHub ]

# File 'lib/csv.rb', line 1412


def build_fields_converter(initial_converters, options)
  fields_converter = FieldsConverter.new(options)
  normalize_converters(initial_converters).each do |name, converter|
    fields_converter.add_converter(name, &converter)
  end
  fields_converter
end

#build_header_fields_converter (private)

[ GitHub ]

# File 'lib/csv.rb', line 1394


def build_header_fields_converter
  specific_options = {
    builtin_converters: HeaderConverters,
    accept_nil: true,
  }
  options = @base_fields_converter_options.merge(specific_options)
  build_fields_converter(@initial_header_converters, options)
end

#build_parser_fields_converter (private)

[ GitHub ]

# File 'lib/csv.rb', line 1382


def build_parser_fields_converter
  specific_options = {
    builtin_converters: Converters,
  }
  options = @base_fields_converter_options.merge(specific_options)
  build_fields_converter(@initial_converters, options)
end

#build_writer_fields_converter (private)

[ GitHub ]

# File 'lib/csv.rb', line 1407


def build_writer_fields_converter
  build_fields_converter(@initial_write_converters,
                         @write_fields_converter_options)
end

#col_sep

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

[ GitHub ]

# File 'lib/csv.rb', line 979


def col_sep
  parser.column_separator
end

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

You can use this method to install a 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.

[ GitHub ]

# File 'lib/csv.rb', line 1207


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

#convert_fields(fields, headers = false) (private)

Processes fields with @converters, or @header_converters if #headers is passed as true, returning the converted field set. Any converter that changes the field into something other than a ::String halts the pipeline of conversion for that field. This is primarily an efficiency shortcut.

[ GitHub ]

# File 'lib/csv.rb', line 1357


def convert_fields(fields, headers = false)
  if headers
    header_fields_converter.convert(fields, nil, 0)
  else
    parser_fields_converter.convert(fields, @headers, lineno)
  end
end

#converters

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

[ GitHub ]

# File 'lib/csv.rb', line 1014


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

#determine_encoding(encoding, internal_encoding) (private)

[ GitHub ]

# File 'lib/csv.rb', line 1320


def determine_encoding(encoding, internal_encoding)
  # honor the IO encoding if we can, otherwise default to ASCII-8BIT
  io_encoding = raw_encoding
  return io_encoding if io_encoding

  return Encoding.find(internal_encoding) if internal_encoding

  if encoding
    encoding, = encoding.split(":", 2) if encoding.is_a?(String)
    return Encoding.find(encoding)
  end

  Encoding.default_internal || Encoding.default_external
end

#each(&block)

Yields each row of the data source in turn.

Support for Enumerable.

The data source must be open for reading.

[ GitHub ]

# File 'lib/csv.rb', line 1235


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

#eof? ⇒ `Boolean` (readonly) Also known as: #eof

[ GitHub ]

# File 'lib/csv.rb', line 1158


def eof?
  begin
    parser_enumerator.peek
    false
  rescue StopIteration
    true
  end
end

#field_size_limit

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

[ GitHub ]

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


def field_size_limit
  parser.field_size_limit
end

#flock(*args)

Raises:

(NotImplementedError)

[ GitHub ]

# File 'lib/csv.rb', line 1130


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

#gets

Alias for #shift.

[ GitHub ]

# File 'lib/csv.rb', line 1273


alias_method :gets,     :shift

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

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

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

[ GitHub ]

# File 'lib/csv.rb', line 1222


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

#header_converters

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

[ GitHub ]

# File 'lib/csv.rb', line 1062


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

#header_fields_converter (private)

[ GitHub ]

# File 'lib/csv.rb', line 1390


def header_fields_converter
  @header_fields_converter ||= build_header_fields_converter
end

#headers

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 .new for details.

[ GitHub ]

# File 'lib/csv.rb', line 1033


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

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

[ GitHub ]

# File 'lib/csv.rb', line 1280


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)

Raises:

(NotImplementedError)

[ GitHub ]

# File 'lib/csv.rb', line 1135


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

#line

The last row read from this file.

[ GitHub ]

# File 'lib/csv.rb', line 1108


def line
  parser.line
end

#lineno

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

[ GitHub ]

# File 'lib/csv.rb', line 1097


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

#normalize_converters(converters) (private)

[ GitHub ]

# File 'lib/csv.rb', line 1335


def normalize_converters(converters)
  converters ||= []
  unless converters.is_a?(Array)
    converters = [converters]
  end
  converters.collect do |converter|
    case converter
    when Proc # custom code block
      [nil, converter]
    else # by name
      [converter, nil]
    end
  end
end

#parser (private)

[ GitHub ]

# File 'lib/csv.rb', line 1420


def parser
  @parser ||= Parser.new(@io, parser_options)
end

#parser_enumerator (private)

[ GitHub ]

# File 'lib/csv.rb', line 1429


def parser_enumerator
  @parser_enumerator ||= parser.parse
end

#parser_fields_converter (private)

[ GitHub ]

# File 'lib/csv.rb', line 1378


def parser_fields_converter
  @parser_fields_converter ||= build_parser_fields_converter
end

#parser_options (private)

[ GitHub ]

# File 'lib/csv.rb', line 1424


def parser_options
  @parser_options.merge(header_fields_converter: header_fields_converter,
                        fields_converter: parser_fields_converter)
end

#path

[ GitHub ]

# File 'lib/csv.rb', line 1140


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

#puts(row)

Alias for #<<.

[ GitHub ]

# File 'lib/csv.rb', line 1190


alias_method :puts,    :<<

#quote_char

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

[ GitHub ]

# File 'lib/csv.rb', line 995


def quote_char
  parser.quote_character
end

#raw_encoding (private)

Returns the encoding of the internal IO object.

[ GitHub ]

# File 'lib/csv.rb', line 1368


def raw_encoding
  if @io.respond_to? :internal_encoding
    @io.internal_encoding || @io.external_encoding
  elsif @io.respond_to? :encoding
    @io.encoding
  else
    nil
  end
end

#read Also known as: #readlines

Slurps the remaining rows and returns an ::Array of Arrays.

The data source must be open for reading.

[ GitHub ]

# File 'lib/csv.rb', line 1244


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

#readline

Alias for #shift.

[ GitHub ]

# File 'lib/csv.rb', line 1274


alias_method :readline, :shift

#readlines

Alias for #read.

[ GitHub ]

# File 'lib/csv.rb', line 1252


alias_method :readlines, :read

#rewind

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

[ GitHub ]

# File 'lib/csv.rb', line 1169


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

#row_sep

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

[ GitHub ]

# File 'lib/csv.rb', line 987


def row_sep
  parser.row_separator
end

#shift 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.

[ GitHub ]

# File 'lib/csv.rb', line 1266


def shift
  begin
    parser_enumerator.next
  rescue StopIteration
    nil
  end
end

#skip_lines

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

[ GitHub ]

# File 'lib/csv.rb', line 1005


def skip_lines
  parser.skip_lines
end

#stat(*args)

Raises:

(NotImplementedError)

[ GitHub ]

# File 'lib/csv.rb', line 1144


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

#to_i

Raises:

(NotImplementedError)

[ GitHub ]

# File 'lib/csv.rb', line 1149


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

#to_io

[ GitHub ]

# File 'lib/csv.rb', line 1154


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

#writer (private)

[ GitHub ]

# File 'lib/csv.rb', line 1433


def writer
  @writer ||= Writer.new(@io, writer_options)
end

#writer_fields_converter (private)

[ GitHub ]

# File 'lib/csv.rb', line 1403


def writer_fields_converter
  @writer_fields_converter ||= build_writer_fields_converter
end

#writer_options (private)

[ GitHub ]

# File 'lib/csv.rb', line 1437


def writer_options
  @writer_options.merge(header_fields_converter: header_fields_converter,
                        fields_converter: writer_fields_converter)
end

Class: CSV

Overview

Specialized Methods

Reading

Writing

Shortcuts

Data Conversion

CSV with headers

Typed data reading

CSV and Character Encodings (M17n or Multilingualization)

Constant Summary

Class Method Summary

Instance Attribute Summary

Instance Method Summary

Constructor Details

Class Method Details

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

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

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

.generate_line(row, **options)

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

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

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

.parse_line(line, **options)

.read(path, *options)

.readlines(*args)

.table(path, **options)

Instance Attribute Details

#binmode? ⇒ Boolean (readonly)

#encoding (readonly)

#eof (readonly)

#force_quotes? ⇒ Boolean (readonly)

#header_row? ⇒ Boolean (readonly)

#liberal_parsing? ⇒ Boolean (readonly)

#return_headers? ⇒ Boolean (readonly)

#skip_blanks? ⇒ Boolean (readonly)

#unconverted_fields? ⇒ Boolean (readonly)

#write_headers? ⇒ Boolean (readonly)

Instance Method Details

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

#add_row(row)

#build_fields_converter(initial_converters, options) (private)

#build_header_fields_converter (private)

#build_parser_fields_converter (private)

#build_writer_fields_converter (private)

#col_sep

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

#convert_fields(fields, headers = false) (private)

#converters

#determine_encoding(encoding, internal_encoding) (private)

#each(&block)

#eof? ⇒ Boolean (readonly) Also known as: #eof

#field_size_limit

#flock(*args)

#gets

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

#header_converters

#header_fields_converter (private)

#headers

#inspect

#ioctl(*args)

#line

#lineno

#normalize_converters(converters) (private)

#parser (private)

#parser_enumerator (private)

#parser_fields_converter (private)

#parser_options (private)

#path

#puts(row)

#quote_char

#raw_encoding (private)

#read Also known as: #readlines

#readline

#readlines

#rewind

#row_sep

#shift Also known as: #gets, #readline

#skip_lines

#stat(*args)

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

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

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

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

#binmode? ⇒ `Boolean` (readonly)

#force_quotes? ⇒ `Boolean` (readonly)

#header_row? ⇒ `Boolean` (readonly)

#liberal_parsing? ⇒ `Boolean` (readonly)

#return_headers? ⇒ `Boolean` (readonly)

#skip_blanks? ⇒ `Boolean` (readonly)

#unconverted_fields? ⇒ `Boolean` (readonly)

#write_headers? ⇒ `Boolean` (readonly)

#eof? ⇒ `Boolean` (readonly) Also known as: #eof