End of Life Ruby 3.0 has reached end of life and gets no more fixes. Switch to Ruby 4.0 →

class method

CSV.open

open(file_path, mode = "rb", **options ) → new_csv

open(io, mode = "rb", **options ) → new_csv

open(file_path, mode = "rb", **options ) { |csv| ... } → object

open(io, mode = "rb", **options ) { |csv| ... } → object

# File tmp/rubies/ruby-3.0.5/lib/csv.rb, line 1412
def open(filename, mode="r", **options)
  # wrap a File opened with the remaining +args+ with no newline
  # decorator
  file_opts = {universal_newline: false}.merge(options)
  options.delete(:invalid)
  options.delete(:undef)
  options.delete(:replace)

  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

possible options elements:

hash form:
  :invalid => nil      # raise error on invalid byte sequence (default)
  :invalid => :replace # replace invalid byte sequence
  :undef => :replace   # replace undefined conversion
  :replace => string   # replacement string ("?" or "\uFFFD" if not specified)

Argument path, if given, must be the path to a file.
Argument io should be an IO object that is:
- Open for reading; on return, the IO object will be closed.
- Positioned at the beginning. To position at the end, for appending, use method CSV.generate. For any other positioning, pass a preset StringIO object instead.
Argument mode, if given, must be a File mode See Open Mode.
Arguments **options must be keyword options. See Options for Generating.
This method optionally accepts an additional :encoding option that you can use to specify the Encoding of the data read from path or io. You must provide this unless your data is in the encoding given by Encoding::default_external. Parsing 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 parsing.

These examples assume prior execution of:

Example

string = "foo,0\nbar,1\nbaz,2\n"
path = 't.csv'
File.write(path, string)

With no block given, returns a new CSV object.

Create a CSV object using a file path:

Example

csv = CSV.open(path)
csv # => #<CSV io_type:File io_path:"t.csv" encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">

Create a CSV object using an open File:

Example

csv = CSV.open(File.open(path))
csv # => #<CSV io_type:File io_path:"t.csv" encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">

With a block given, calls the block with the created CSV object; returns the block’s return value:

Using a file path:

Example

csv = CSV.open(path) {|csv| p csv}
csv # => #<CSV io_type:File io_path:"t.csv" encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">

Output:

Example

#<CSV io_type:File io_path:"t.csv" encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">

Using an open File:

Example

csv = CSV.open(File.open(path)) {|csv| p csv}
csv # => #<CSV io_type:File io_path:"t.csv" encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">

Output:

Example

#<CSV io_type:File io_path:"t.csv" encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">

Raises an exception if the argument is not a String object or IO object:

Example

# Raises TypeError (no implicit conversion of Symbol into String)
CSV.open(:foo)

See also .new .parse .instance .parse_line also in 3.3 · 3.2 · 3.1

‹ prev.new next ›.parse