CSV

Class

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.

Reading

From a `File`

A Line at a `Time`

CSV.foreach("path/to/file.csv") do |row|
  # use row here...
end

All at Once

arr_of_arrs = CSV.read("path/to/file.csv")

From a String

A Line at a `Time`

CSV.parse("CSV,data,String") do |row|
  # use row here...
end

All at Once

arr_of_arrs = CSV.parse("CSV,data,String")

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

Convert a Single Line

csv_string = ["CSV", "data"].to_csv   # to CSV
csv_array  = "CSV,String".parse_csv   # from CSV

Shortcut Interface

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

Advanced Usage

Wrap an `IO` `Object`

csv = CSV.new(io, options)
# ... read (with gets() or each()) from and write (with <<) to csv here ...

`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.

Constants

VERSION

The version of the installed library.

FieldInfo

A FieldInfo Struct contains details about a field’s position in the data source it was read from. CSV will pass this Struct to some blocks that make decisions based on field structure. See CSV.convert_fields() for an example.

index: The zero-based index of the field in its row.
line: The line of the data source this row is from.
header: The header for the column, when available.

DateMatcher

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

DateTimeMatcher

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

ConverterEncoding

The encoding used by all converters.

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.

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: The header String is downcased, 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.

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

Attributes

col_sep

Read

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

row_sep

Read

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

quote_char

Read

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

field_size_limit

Read

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

skip_lines

Read

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

encoding

Read

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.

lineno

Read

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

Class Methods

filter( options = Hash.new ) { |row| ... }

filter( input, options = Hash.new ) { |row| ... }

filter( input, output, options = Hash.new ) { |row| ... }

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1087
def self.filter(*args)
  # parse options for input, output, or both
  in_options, out_options = Hash.new, {row_sep: $INPUT_RECORD_SEPARATOR}
  if args.last.is_a? Hash
    args.pop.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
  end
  # build input and output wrappers
  input  = new(args.shift || ARGF,    in_options)
  output = new(args.shift || $stdout, out_options)

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

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.

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

foreach(path, options = Hash.new, &block)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1128
def self.foreach(path, options = Hash.new, &block)
  return to_enum(__method__, path, options) unless block
  open(path, options) do |csv|
    csv.each(&block)
  end
end

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 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.

generate( str, options = Hash.new ) { |csv| ... }

generate( options = Hash.new ) { |csv| ... }

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1153
def self.generate(*args)
  # add a default empty String, if none was given
  if args.first.is_a? String
    io = StringIO.new(args.shift)
    io.seek(0, IO::SEEK_END)
    args.unshift(io)
  else
    encoding = args[-1][:encoding] if args.last.is_a?(Hash)
    str      = String.new
    str.force_encoding(encoding) if encoding
    args.unshift(str)
  end
  csv = new(*args)  # wrap
  yield csv         # yield for appending
  csv.string        # return final String
end

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 CSV::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.

generate_line(row, options = Hash.new)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1183
def self.generate_line(row, options = Hash.new)
  options  = {row_sep: $INPUT_RECORD_SEPARATOR}.merge(options)
  encoding = options.delete(:encoding)
  str      = String.new
  if encoding
    str.force_encoding(encoding)
  elsif field = row.find { |f| not f.nil? }
    str.force_encoding(String(field).encoding)
  end
  (new(str, options) << row).string
end

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

The options parameter can be anything CSV::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.

instance(data = $stdout, options = Hash.new) { |instance| ... }

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1047
def self.instance(data = $stdout, options = Hash.new)
  # 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

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.

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

new(data, options = Hash.new)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1508
def initialize(data, options = Hash.new)
  if data.nil?
    raise ArgumentError.new("Cannot parse nil as CSV")
  end

  # build the options for this read/write
  options = DEFAULT_OPTIONS.merge(options)

  # create the IO object we will read from
  @io       = data.is_a?(String) ? StringIO.new(data) : data
  # honor the IO encoding if we can, otherwise default to ASCII-8BIT
  @encoding = raw_encoding(nil) ||
              ( if encoding = options.delete(:internal_encoding)
                  case encoding
                  when Encoding; encoding
                  else Encoding.find(encoding)
                  end
                end ) ||
              ( case encoding = options.delete(:encoding)
                when Encoding; encoding
                when /\A[^:]+/; Encoding.find($&)
                end ) ||
              Encoding.default_internal || Encoding.default_external
  #
  # prepare for building safe regular expressions in the target encoding,
  # if we can transcode the needed characters
  #
  @re_esc   =   "\\".encode(@encoding).freeze rescue ""
  @re_chars =   /#{%"[-\\]\\[\\.^$?*+{}()|# \r\n\t\f\v]".encode(@encoding)}/

  init_separators(options)
  init_parsers(options)
  init_converters(options)
  init_headers(options)
  init_comments(options)

  @force_encoding = !!(encoding || options.delete(:encoding))
  options.delete(:internal_encoding)
  options.delete(:external_encoding)
  unless options.empty?
    raise ArgumentError, "Unknown options:  #{options.keys.join(', ')}."
  end

  # track our own lineno since IO gets confused about line-ends is CSV fields
  @lineno = 0
end

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.

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.

See CSV::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.

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

open( filename, options = Hash.new ) { |faster_csv| ... }

open( filename, mode = "rb", options = Hash.new )

open( filename, options = Hash.new )

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1258
def self.open(*args)
  # find the +options+ Hash
  options = if args.last.is_a? Hash then args.pop else Hash.new end
  # wrap a File opened with the remaining +args+ with no newline
  # decorator
  file_opts = {universal_newline: false}.merge(options)
  begin
    f = File.open(*args, file_opts)
  rescue ArgumentError => e
    raise unless /needs binmode/ =~ e.message and args.size == 1
    args << "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

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 CSV::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 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?()

parse( str, options = Hash.new ) { |row| ... }

parse( str, options = Hash.new )

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1303
def self.parse(*args, &block)
  csv = new(*args)
  if block.nil?  # slurp contents, if no block is given
    begin
      csv.read
    ensure
      csv.close
    end
  else           # or pass each row to a provided block
    csv.each(&block)
  end
end

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 Hash containing anything CSV::new() understands.

parse_line(line, options = Hash.new)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1323
def self.parse_line(line, options = Hash.new)
  new(line, options).shift
end

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 CSV::new() understands.

read(path, *options)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1338
def self.read(path, *options)
  open(path, *options) { |csv| csv.read }
end

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

readlines(*args)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1343
def self.readlines(*args)
  read(*args)
end

Alias for CSV::read().

table(path, options = Hash.new)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1354
def self.table(path, options = Hash.new)
  read( path, { headers:           true,
                converters:        :numeric,
                header_converters: :symbol }.merge(options) )
end

A shortcut for:

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

Instance Methods

<<(row)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1665
def <<(row)
  # make sure headers have been assigned
  if header_row? and [Array, String].include? @use_headers.class
    parse_headers  # won't read data for Array or String
    self << @headers if @write_headers
  end

  # handle CSV::Row objects and Hashes
  row = case row
        when self.class::Row then row.fields
        when Hash            then @headers.map { |header| row[header] }
        else                      row
        end

  @headers =  row if header_row?
  @lineno  += 1

  output = row.map(&@quote).join(@col_sep) + @row_sep  # quote and separate
  if @io.is_a?(StringIO)             and
     output.encoding != (encoding = raw_encoding)
    if @force_encoding
      output = output.encode(encoding)
    elsif (compatible_encoding = Encoding.compatible?(@io.string, output))
      @io.set_encoding(compatible_encoding)
      @io.seek(0, IO::SEEK_END)
    end
  end
  @io << output

  self  # for chaining
end

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.

add_converter(var_name, const, name = nil, &converter)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 2171
def add_converter(var_name, const, name = nil, &converter)
  if name.nil?  # custom converter
    instance_variable_get("@#{var_name}") << converter
  else          # named converter
    combo = const[name]
    case combo
    when Array  # combo converter
      combo.each do |converter_name|
        add_converter(var_name, const, converter_name)
      end
    else        # individual named converter
      instance_variable_get("@#{var_name}") << combo
    end
  end
end

The actual work method for adding converters, used by both CSV.convert() and CSV.header_convert().

This method requires the var_name of the instance variable to place the converters in, the const Hash to lookup named converters in, and the normal parameters of the CSV.convert() and CSV.header_convert() methods.

add_row(row)

lib/csv.rb View on GitHub

An alias for <<

add_unconverted_fields(row, fields)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 2258
def add_unconverted_fields(row, fields)
  class << row
    attr_reader :unconverted_fields
  end
  row.instance_eval { @unconverted_fields = fields }
  row
end

This method injects an instance variable unconverted_fields into row and an accessor method for row called unconverted_fields(). The variable is set to the contents of fields.

convert( name )

convert { |field| ... }

convert { |field, field_info| ... }

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1714
def convert(name = nil, &converter)
  add_converter(:converters, self.class::Converters, name, &converter)
end

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.

convert_fields(fields, headers = false)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 2194
def convert_fields(fields, headers = false)
  # see if we are converting headers or fields
  converters = headers ? @header_converters : @converters

  fields.map.with_index do |field, index|
    converters.each do |converter|
      break if field.nil?
      field = if converter.arity == 1  # straight field converter
        converter[field]
      else                             # FieldInfo converter
        header = @use_headers && !headers ? @headers[index] : nil
        converter[field, FieldInfo.new(index, lineno, header)]
      end
      break unless field.is_a? String  # short-circuit pipeline for speed
    end
    field  # final state of each field, converted or original
  end
end

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.

converters

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1581
def converters
  @converters.map do |converter|
    name = Converters.rassoc(converter)
    name ? name.first : converter
  end
end

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.

each() { |row| ... }

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1745
def each
  if block_given?
    while row = shift
      yield row
    end
  else
    to_enum
  end
end

Yields each row of the data source in turn.

Support for Enumerable.

The data source must be open for reading.

encode_re(*chunks)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 2281
def encode_re(*chunks)
  Regexp.new(encode_str(*chunks))
end

Builds a regular expression in @encoding. All chunks will be transcoded to that encoding.

encode_str(*chunks)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 2289
def encode_str(*chunks)
  chunks.map { |chunk| chunk.encode(@encoding.name) }.join('')
end

Builds a String in @encoding. All chunks will be transcoded to that encoding.

escape_re(str)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 2273
def escape_re(str)
  str.gsub(@re_chars) {|c| @re_esc + c}
end

This method is an encoding safe version of Regexp::escape(). It will escape any characters that would change the meaning of a regular expression in the encoding of str. Regular expression characters that cannot be transcoded to the target encoding will be skipped and no escaping will be performed if a backslash cannot be transcoded.

force_quotes?

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1624
def force_quotes?()       @force_quotes       end

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

gets

lib/csv.rb View on GitHub

An alias for shift

header_convert( name )

header_convert { |field| ... }

header_convert { |field, field_info| ... }

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1729
def header_convert(name = nil, &converter)
  add_converter( :header_converters,
                 self.class::HeaderConverters,
                 name,
                 &converter )
end

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

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

header_converters

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1612
def header_converters
  @header_converters.map do |converter|
    name = HeaderConverters.rassoc(converter)
    name ? name.first : converter
  end
end

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.

header_row?

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1771
def header_row?
  @use_headers and @headers.nil?
end

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

headers

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1597
def headers
  @headers || true if @use_headers
end

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.

init_comments(options)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 2156
def init_comments(options)
  @skip_lines = options.delete(:skip_lines)
  @skip_lines = Regexp.new(@skip_lines) if @skip_lines.is_a? String
  if @skip_lines and not @skip_lines.respond_to?(:match)
    raise ArgumentError, ":skip_lines has to respond to matches"
  end
end

Stores the pattern of comments to skip from the provided options.

The pattern must respond to .match, else ArgumentError is raised. Strings are converted to a Regexp.

init_converters(options, field_name = :converters)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 2109
def init_converters(options, field_name = :converters)
  if field_name == :converters
    @unconverted_fields = options.delete(:unconverted_fields)
  end

  instance_variable_set("@#{field_name}", Array.new)

  # find the correct method to add the converters
  convert = method(field_name.to_s.sub(/ers\Z/, ""))

  # load converters
  unless options[field_name].nil?
    # allow a single converter not wrapped in an Array
    unless options[field_name].is_a? Array
      options[field_name] = [options[field_name]]
    end
    # load each converter...
    options[field_name].each do |converter|
      if converter.is_a? Proc  # custom code block
        convert.call(&converter)
      else                     # by name
        convert.call(converter)
      end
    end
  end

  options.delete(field_name)
end

Loads any converters requested during construction.

If field_name is set :converters (the default) field converters are set. When field_name is :header_converters header converters are added instead.

The :unconverted_fields option is also activated for :converters calls, if requested.

init_headers(options)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 2139
def init_headers(options)
  @use_headers    = options.delete(:headers)
  @return_headers = options.delete(:return_headers)
  @write_headers  = options.delete(:write_headers)

  # headers must be delayed until shift(), in case they need a row of content
  @headers = nil

  init_converters(options, :header_converters)
end

Stores header row settings and loads header converters, if needed.

init_parsers(options)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 2078
def init_parsers(options)
  # store the parser behaviors
  @skip_blanks      = options.delete(:skip_blanks)
  @field_size_limit = options.delete(:field_size_limit)

  # prebuild Regexps for faster parsing
  esc_row_sep = escape_re(@row_sep)
  esc_quote   = escape_re(@quote_char)
  @parsers = {
    # for detecting parse errors
    quote_or_nl:    encode_re("[", esc_quote, "\r\n]"),
    nl_or_lf:       encode_re("[\r\n]"),
    stray_quote:    encode_re( "[^", esc_quote, "]", esc_quote,
                               "[^", esc_quote, "]" ),
    # safer than chomp!()
    line_end:       encode_re(esc_row_sep, "\\z"),
    # illegal unquoted characters
    return_newline: encode_str("\r\n")
  }
end

Pre-compiles parsers and stores them by name for access during reads.

init_separators(options)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1979
def init_separators(options)
  # store the selected separators
  @col_sep    = options.delete(:col_sep).to_s.encode(@encoding)
  @row_sep    = options.delete(:row_sep)  # encode after resolving :auto
  @quote_char = options.delete(:quote_char).to_s.encode(@encoding)

  if @quote_char.length != 1
    raise ArgumentError, ":quote_char has to be a single character String"
  end

  #
  # automatically discover row separator when requested
  # (not fully encoding safe)
  #
  if @row_sep == :auto
    if [ARGF, STDIN, STDOUT, STDERR].include?(@io) or
       (defined?(Zlib) and @io.class == Zlib::GzipWriter)
      @row_sep = $INPUT_RECORD_SEPARATOR
    else
      begin
        #
        # remember where we were (pos() will raise an exception if @io is pipe
        # or not opened for reading)
        #
        saved_pos = @io.pos
        while @row_sep == :auto
          #
          # if we run out of data, it's probably a single line
          # (ensure will set default value)
          #
          break unless sample = @io.gets(nil, 1024)
          # extend sample if we're unsure of the line ending
          if sample.end_with? encode_str("\r")
            sample << (@io.gets(nil, 1) || "")
          end

          # try to find a standard separator
          if sample =~ encode_re("\r\n?|\n")
            @row_sep = $&
            break
          end
        end

        # tricky seek() clone to work around GzipReader's lack of seek()
        @io.rewind
        # reset back to the remembered position
        while saved_pos > 1024  # avoid loading a lot of data into memory
          @io.read(1024)
          saved_pos -= 1024
        end
        @io.read(saved_pos) if saved_pos.nonzero?
      rescue IOError         # not opened for reading
        # do nothing:  ensure will set default
      rescue NoMethodError   # Zlib::GzipWriter doesn't have some IO methods
        # do nothing:  ensure will set default
      rescue SystemCallError # pipe
        # do nothing:  ensure will set default
      ensure
        #
        # set default if we failed to detect
        # (stream not opened for reading, a pipe, or a single line of data)
        #
        @row_sep = $INPUT_RECORD_SEPARATOR if @row_sep == :auto
      end
    end
  end
  @row_sep = @row_sep.to_s.encode(@encoding)

  # establish quoting rules
  @force_quotes   = options.delete(:force_quotes)
  do_quote        = lambda do |field|
    field         = String(field)
    encoded_quote = @quote_char.encode(field.encoding)
    encoded_quote                                +
    field.gsub(encoded_quote, encoded_quote * 2) +
    encoded_quote
  end
  quotable_chars = encode_str("\r\n", @col_sep, @quote_char)
  @quote         = if @force_quotes
    do_quote
  else
    lambda do |field|
      if field.nil?  # represent +nil+ fields as empty unquoted fields
        ""
      else
        field = String(field)  # Stringify fields
        # represent empty fields as empty quoted fields
        if field.empty? or
           field.count(quotable_chars).nonzero?
          do_quote.call(field)
        else
          field  # unquoted field
        end
      end
    end
  end
end

Stores the indicated separators for later use.

If auto-discovery was requested for @row_sep, this method will read ahead in the @io and try to find one. ARGF, STDIN, STDOUT, STDERR and any stream open for output only with a default @row_sep of $INPUT_RECORD_SEPARATOR ($/).

This method also establishes the quoting rules used for CSV output.

inspect

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1932
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
  %w[ lineno     col_sep     row_sep
      quote_char skip_blanks ].each do |attr_name|
    if a = instance_variable_get("@#{attr_name}")
      str << " " << attr_name << ":" << a.inspect
    end
  end
  if @use_headers
    str << " headers:" << headers.inspect
  end
  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

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

parse_headers(row = nil)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 2223
def parse_headers(row = nil)
  if @headers.nil?                # header row
    @headers = case @use_headers  # save headers
               # Array of headers
               when Array then @use_headers
               # CSV header String
               when String
                 self.class.parse_line( @use_headers,
                                        col_sep:    @col_sep,
                                        row_sep:    @row_sep,
                                        quote_char: @quote_char )
               # first row is headers
               else            row
               end

    # prepare converted and unconverted copies
    row      = @headers                       if row.nil?
    @headers = convert_fields(@headers, true)
    @headers.each { |h| h.freeze if h.is_a? String }

    if @return_headers                                     # return headers
      return self.class::Row.new(@headers, row, true)
    elsif not [Array, String].include? @use_headers.class  # skip to field row
      return shift
    end
  end

  self.class::Row.new(@headers, convert_fields(row))  # field row
end

This method is used to turn a finished row into a CSV::Row. Header rows are also dealt with here, either by returning a CSV::Row with identical headers and fields (save that the fields do not go through the converters) or by reading past them to return a field row. Headers are also saved in @headers for use in future rows.

When nil, row is assumed to be a header row not based on an actual row of the stream.

puts(row)

lib/csv.rb View on GitHub

An alias for <<

raw_encoding(default = Encoding::ASCII_8BIT)

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 2299
def raw_encoding(default = Encoding::ASCII_8BIT)
  if @io.respond_to? :internal_encoding
    @io.internal_encoding || @io.external_encoding
  elsif @io.is_a? StringIO
    @io.string.encoding
  elsif @io.respond_to? :encoding
    @io.encoding
  else
    default
  end
end

Returns the encoding of the internal IO object or the default if the encoding cannot be determined.

read

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1760
def read
  rows = to_a
  if @use_headers
    Table.new(rows)
  else
    rows
  end
end

Slurps the remaining rows and returns an Array of Arrays.

The data source must be open for reading.

readline

lib/csv.rb View on GitHub

An alias for shift

readlines

lib/csv.rb View on GitHub

An alias for read

return_headers?

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1604
def return_headers?()     @return_headers     end

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

rewind

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1649
def rewind
  @headers = nil
  @lineno  = 0

  @io.rewind
end

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

shift

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1782
def shift
  #########################################################################
  ### This method is purposefully kept a bit long as simple conditional ###
  ### checks are faster than numerous (expensive) method calls.         ###
  #########################################################################

  # handle headers not based on document content
  if header_row? and @return_headers and
     [Array, String].include? @use_headers.class
    if @unconverted_fields
      return add_unconverted_fields(parse_headers, Array.new)
    else
      return parse_headers
    end
  end

  #
  # it can take multiple calls to <tt>@io.gets()</tt> to get a full line,
  # because of \r and/or \n characters embedded in quoted fields
  #
  in_extended_col = false
  csv             = Array.new

  loop do
    # add another read to the line
    unless parse = @io.gets(@row_sep)
      return nil
    end

    parse.sub!(@parsers[:line_end], "")

    if csv.empty?
      #
      # I believe a blank line should be an <tt>Array.new</tt>, not Ruby 1.8
      # CSV's <tt>[nil]</tt>
      #
      if parse.empty?
        @lineno += 1
        if @skip_blanks
          next
        elsif @unconverted_fields
          return add_unconverted_fields(Array.new, Array.new)
        elsif @use_headers
          return self.class::Row.new(Array.new, Array.new)
        else
          return Array.new
        end
      end
    end

    next if @skip_lines and @skip_lines.match parse

    parts =  parse.split(@col_sep, -1)
    if parts.empty?
      if in_extended_col
        csv[-1] << @col_sep   # will be replaced with a @row_sep after the parts.each loop
      else
        csv << nil
      end
    end

    # This loop is the hot path of csv parsing. Some things may be non-dry
    # for a reason. Make sure to benchmark when refactoring.
    parts.each do |part|
      if in_extended_col
        # If we are continuing a previous column
        if part[-1] == @quote_char && part.count(@quote_char) % 2 != 0
          # extended column ends
          csv.last << part[0..-2]
          if csv.last =~ @parsers[:stray_quote]
            raise MalformedCSVError,
                  "Missing or stray quote in line #{lineno + 1}"
          end
          csv.last.gsub!(@quote_char * 2, @quote_char)
          in_extended_col = false
        else
          csv.last << part
          csv.last << @col_sep
        end
      elsif part[0] == @quote_char
        # If we are starting a new quoted column
        if part[-1] != @quote_char || part.count(@quote_char) % 2 != 0
          # start an extended column
          csv             << part[1..-1]
          csv.last        << @col_sep
          in_extended_col =  true
        else
          # regular quoted column
          csv << part[1..-2]
          if csv.last =~ @parsers[:stray_quote]
            raise MalformedCSVError,
                  "Missing or stray quote in line #{lineno + 1}"
          end
          csv.last.gsub!(@quote_char * 2, @quote_char)
        end
      elsif part =~ @parsers[:quote_or_nl]
        # Unquoted field with bad characters.
        if part =~ @parsers[:nl_or_lf]
          raise MalformedCSVError, "Unquoted fields do not allow " +
                                   "\\r or \\n (line #{lineno + 1})."
        else
          raise MalformedCSVError, "Illegal quoting in line #{lineno + 1}."
        end
      else
        # Regular ole unquoted field.
        csv << (part.empty? ? nil : part)
      end
    end

    # Replace tacked on @col_sep with @row_sep if we are still in an extended
    # column.
    csv[-1][-1] = @row_sep if in_extended_col

    if in_extended_col
      # if we're at eof?(), a quoted field wasn't closed...
      if @io.eof?
        raise MalformedCSVError,
              "Unclosed quoted field on line #{lineno + 1}."
      elsif @field_size_limit and csv.last.size >= @field_size_limit
        raise MalformedCSVError, "Field size exceeded on line #{lineno + 1}."
      end
      # otherwise, we need to loop and pull some more data to complete the row
    else
      @lineno += 1

      # save fields unconverted fields, if needed...
      unconverted = csv.dup if @unconverted_fields

      # convert fields, if needed...
      csv = convert_fields(csv) unless @use_headers or @converters.empty?
      # parse out header rows and handle CSV::Row conversions...
      csv = parse_headers(csv)  if     @use_headers

      # inject unconverted fields and accessor, if requested...
      if @unconverted_fields and not csv.respond_to? :unconverted_fields
        add_unconverted_fields(csv, unconverted)
      end

      # return the results
      break csv
    end
  end
end

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.

skip_blanks?

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1622
def skip_blanks?()        @skip_blanks        end

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

unconverted_fields?

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1591
def unconverted_fields?() @unconverted_fields end

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

write_headers?

lib/csv.rb View on GitHub

          
            # File tmp/rubies/ruby-2.3.8/lib/csv.rb, line 1606
def write_headers?()      @write_headers      end

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

Reading

From a File

A Line at a Time

All at Once

From a String

A Line at a Time

All at Once

Writing

To a File

To a String

Convert a Single Line

Shortcut Interface

Advanced Usage

Wrap an IO Object

CSV and Character Encodings (M17n or Multilingualization)

filter( options = Hash.new ) { |row| ... }

filter( input, options = Hash.new ) { |row| ... }

filter( input, output, options = Hash.new ) { |row| ... }

foreach(path, options = Hash.new, &block)

generate( str, options = Hash.new ) { |csv| ... }

generate( options = Hash.new ) { |csv| ... }

generate_line(row, options = Hash.new)

instance(data = $stdout, options = Hash.new) { |instance| ... }

new(data, options = Hash.new)

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

open( filename, options = Hash.new ) { |faster_csv| ... }

open( filename, mode = "rb", options = Hash.new )

open( filename, options = Hash.new )

parse( str, options = Hash.new ) { |row| ... }

parse( str, options = Hash.new )

parse_line(line, options = Hash.new)

read(path, *options)

readlines(*args)

table(path, options = Hash.new)

<<(row)

add_converter(var_name, const, name = nil, &converter)

add_row(row)

add_unconverted_fields(row, fields)

convert( name )

convert { |field| ... }

convert { |field, field_info| ... }

convert_fields(fields, headers = false)

converters

each() { |row| ... }

encode_re(*chunks)

encode_str(*chunks)

escape_re(str)

force_quotes?

gets

header_convert( name )

header_convert { |field| ... }

header_convert { |field, field_info| ... }

header_converters

header_row?

headers

init_comments(options)

init_converters(options, field_name = :converters)

init_headers(options)

init_parsers(options)

init_separators(options)

inspect

parse_headers(row = nil)

puts(row)

raw_encoding(default = Encoding::ASCII_8BIT)

read

readline

readlines

return_headers?

rewind

shift

skip_blanks?

unconverted_fields?

write_headers?

From a `File`

A Line at a `Time`

A Line at a `Time`

To a `File`

Wrap an `IO` `Object`

`CSV` and Character Encodings (M17n or Multilingualization)