CSV.filter

filter(in_string_or_io, **options) {|row| ... } → array_of_arrays or csv_table

filter(in_string_or_io, out_string_or_io, **options) {|row| ... } → array_of_arrays or csv_table

filter(**options) {|row| ... } → array_of_arrays or csv_table

# File tmp/rubies/ruby-3.3.0/lib/csv.rb, line 1202
def filter(input=nil, output=nil, **options)
  # parse options for input, output, or both
  in_options, out_options = Hash.new, {row_sep: InputRecordSeparator.value}
  options.each do |key, value|
    case key
    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)

  # process headers
  need_manual_header_output =
    (in_options[:headers] and
     out_options[:headers] == true and
     out_options[:write_headers])
  if need_manual_header_output
    first_row = input.shift
    if first_row
      if first_row.is_a?(Row)
        headers = first_row.headers
        yield headers
        output << headers
      end
      yield first_row
      output << first_row
    end
  end

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

Parses CSV from a source (String, IO stream, or ARGF).
Calls the given block with each parsed row:
- Without headers, each row is an Array.
- With headers, each row is a CSV::Row.
Generates CSV to an output (String, IO stream, or STDOUT).
Returns the parsed source:
- Without headers, an Array of Arrays.
- With headers, a CSV::Table.

When in_string_or_io is given, but not out_string_or_io, parses from the given in_string_or_io and generates to STDOUT.

String input without headers:

Example

in_string = "foo,0\nbar,1\nbaz,2"
CSV.filter(in_string) do |row|
  row[0].upcase!
  row[1] = - row[1].to_i
end # => [["FOO", 0], ["BAR", -1], ["BAZ", -2]]

Output (to STDOUT):

FOO,0
BAR,-1
BAZ,-2

String input with headers:

Example

in_string = "Name,Value\nfoo,0\nbar,1\nbaz,2"
CSV.filter(in_string, headers: true) do |row|
  row[0].upcase!
  row[1] = - row[1].to_i
end # => #<CSV::Table mode:col_or_row row_count:4>

Output (to STDOUT):

Name,Value
FOO,0
BAR,-1
BAZ,-2

IO stream input without headers:

Example

File.write('t.csv', "foo,0\nbar,1\nbaz,2")
File.open('t.csv') do |in_io|
  CSV.filter(in_io) do |row|
    row[0].upcase!
    row[1] = - row[1].to_i
  end
end # => [["FOO", 0], ["BAR", -1], ["BAZ", -2]]

Output (to STDOUT):

FOO,0
BAR,-1
BAZ,-2

IO stream input with headers:

Example

File.write('t.csv', "Name,Value\nfoo,0\nbar,1\nbaz,2")
File.open('t.csv') do |in_io|
  CSV.filter(in_io, headers: true) do |row|
    row[0].upcase!
    row[1] = - row[1].to_i
  end
end # => #<CSV::Table mode:col_or_row row_count:4>

Output (to STDOUT):

Name,Value
FOO,0
BAR,-1
BAZ,-2

When both in_string_or_io and out_string_or_io are given, parses from in_string_or_io and generates to out_string_or_io.

String output without headers:

Example

in_string = "foo,0\nbar,1\nbaz,2"
out_string = ''
CSV.filter(in_string, out_string) do |row|
  row[0].upcase!
  row[1] = - row[1].to_i
end # => [["FOO", 0], ["BAR", -1], ["BAZ", -2]]
out_string # => "FOO,0\nBAR,-1\nBAZ,-2\n"

String output with headers:

Example

in_string = "Name,Value\nfoo,0\nbar,1\nbaz,2"
out_string = ''
CSV.filter(in_string, out_string, headers: true) do |row|
  row[0].upcase!
  row[1] = - row[1].to_i
end # => #<CSV::Table mode:col_or_row row_count:4>
out_string # => "Name,Value\nFOO,0\nBAR,-1\nBAZ,-2\n"

IO stream output without headers:

Example

in_string = "foo,0\nbar,1\nbaz,2"
File.open('t.csv', 'w') do |out_io|
  CSV.filter(in_string, out_io) do |row|
    row[0].upcase!
    row[1] = - row[1].to_i
  end
end # => [["FOO", 0], ["BAR", -1], ["BAZ", -2]]
File.read('t.csv') # => "FOO,0\nBAR,-1\nBAZ,-2\n"

IO stream output with headers:

Example

in_string = "Name,Value\nfoo,0\nbar,1\nbaz,2"
File.open('t.csv', 'w') do |out_io|
  CSV.filter(in_string, out_io, headers: true) do |row|
    row[0].upcase!
    row[1] = - row[1].to_i
  end
end # => #<CSV::Table mode:col_or_row row_count:4>
File.read('t.csv') # => "Name,Value\nFOO,0\nBAR,-1\nBAZ,-2\n"

When neither in_string_or_io nor out_string_or_io given, parses from ARGF and generates to STDOUT.

Without headers:

Example

# Put Ruby code into a file.
ruby = <<-EOT
  require 'csv'
  CSV.filter do |row|
    row[0].upcase!
    row[1] = - row[1].to_i
  end
EOT
File.write('t.rb', ruby)
# Put some CSV into a file.
File.write('t.csv', "foo,0\nbar,1\nbaz,2")
# Run the Ruby code with CSV filename as argument.
system(Gem.ruby, "t.rb", "t.csv")

Output (to STDOUT):

FOO,0
BAR,-1
BAZ,-2

With headers:

Example

# Put Ruby code into a file.
ruby = <<-EOT
  require 'csv'
  CSV.filter(headers: true) do |row|
    row[0].upcase!
    row[1] = - row[1].to_i
  end
EOT
File.write('t.rb', ruby)
# Put some CSV into a file.
File.write('t.csv', "Name,Value\nfoo,0\nbar,1\nbaz,2")
# Run the Ruby code with CSV filename as argument.
system(Gem.ruby, "t.rb", "t.csv")

Output (to STDOUT):

Name,Value
FOO,0
BAR,-1
BAZ,-2

Arguments:

Argument in_string_or_io must be a String or an IO stream.
Argument out_string_or_io must be a String or an IO stream.
Arguments **options must be keyword options. See Options for Parsing.

See also .foreach .generate also in 3.2 · 3.1 · 3.0

next ›.foreach