Open and manipulate CSV files in Ruby
By: Vijay
1. To Open a CSV formatted file for reading or writing use
open(path, mode, fs = nil, rs = nil, &block)
For reading.
EXAMPLE 1
CSV.open('csvfile.csv', 'r') do |row| p row end
EXAMPLE 2
reader = CSV.open('csvfile.csv', 'r') row1 = reader.shift row2 = reader.shift if row2.empty? p 'row2 not find.' end reader.close
ARGS
filename: filename to parse. col_sep: Column separator. ?, by default. If you want to separate fields with semicolon, give ?; here. row_sep: Row separator. nil by default. nil means "\r\n or \n". If you want to separate records with \r, give ?\r here.
RETURNS
reader instance. To get parse result, see CSV::Reader#each.
For writing.
EXAMPLE 1
CSV.open('csvfile.csv', 'w') do |writer| writer << ['r1c1', 'r1c2'] writer << ['r2c1', 'r2c2'] writer << [nil, nil] end
EXAMPLE 2
writer = CSV.open('csvfile.csv', 'w') writer << ['r1c1', 'r1c2'] << ['r2c1', 'r2c2'] << [nil, nil] writer.close
ARGS
filename: filename to generate. col_sep: Column separator. ?, by default. If you want to separate fields with semicolon, give ?; here. row_sep: Row separator. nil by default. nil means "\r\n or \n". If you want to separate records with \r, give ?\r here.
RETURNS
writer instance. See CSV::Writer#<< and CSV::Writer#add_row to know how to generate CSV string.
2. Convert a line from cells data to string. Consider using CSV.generate_line instead. To generate multi-row CSV string, see EXAMPLE below.
generate_row(src, cells, out_dev, fs = nil, rs = nil)
EXAMPLE
row1 = ['a', 'b'] row2 = ['c', 'd'] row3 = ['e', 'f'] src = [row1, row2, row3] buf = '' src.each do |row| parsed_cells = CSV.generate_row(row, 2, buf) puts "Created #{ parsed_cells } cells." end p buf
ARGS
src: an Array of String to be converted to CSV string. Must respond to 'size' and '[](idx)'. src[idx] must return String. cells: num of cells in a line. out_dev: buffer for generated CSV string. Must respond to '<<(string)'. col_sep: Column separator. ?, by default. If you want to separate fields with semicolon, give ?; here. row_sep: Row separator. nil by default. nil means "\r\n or \n". If you want to separate records with \r, give ?\r here.
RETURNS
parsed_cells: num of converted cells.
3. parse(str_or_readable, fs = nil, rs = nil) {|row| ...} Parse lines from given string or stream. Return rows as an Array of Arrays.
# File csv.rb, line 115 def CSV.parse(str_or_readable, fs = nil, rs = nil, &block) if File.exist?(str_or_readable) STDERR.puts("CSV.parse(filename) is deprecated." + " Use CSV.open(filename, 'r') instead.") return open_reader(str_or_readable, 'r', fs, rs, &block) end if block CSV::Reader.parse(str_or_readable, fs, rs) do |row| yield(row) end nil else CSV::Reader.create(str_or_readable, fs, rs).collect { |row| row } end end
4. parse_line(src, fs = nil, rs = nil) Parse a line from given string. Bear in mind it parses ONE LINE. Rest of the string is ignored for example "a,b\r\nc,d" => [‘a’, ‘b’] and the second line ‘c,d’ is ignored.
If you don’t know whether a target string to parse is exactly 1 line or not, use CSV.parse_row instead of this method.
# File csv.rb, line 137 def CSV.parse_line(src, fs = nil, rs = nil) fs ||= ',' if fs.is_a?(Fixnum) fs = fs.chr end if !rs.nil? and rs.is_a?(Fixnum) rs = rs.chr end idx = 0 res_type = :DT_COLSEP row = [] begin while res_type == :DT_COLSEP res_type, idx, cell = parse_body(src, idx, fs, rs) row << cell end rescue IllegalFormatError return [] end row end
5. parse_row(src, idx, out_dev, fs = nil, rs = nil) Parse a line from string. Consider using CSV.parse_line instead. To parse lines in CSV string, see EXAMPLE below.
EXAMPLE
src = "a,b\r\nc,d\r\ne,f" idx = 0 begin parsed = [] parsed_cells, idx = CSV.parse_row(src, idx, parsed) puts "Parsed #{ parsed_cells } cells." p parsed end while parsed_cells > 0
ARGS
src: a CSV data to be parsed. Must respond '[](idx)'. src[](idx) must return a char. (Not a string such as 'a', but 97). src[](idx_out_of_bounds) must return nil. A String satisfies this requirement. idx: index of parsing location of 'src'. 0 origin. out_dev: buffer for parsed cells. Must respond '<<(aString)'. col_sep: Column separator. ?, by default. If you want to separate fields with semicolon, give ?; here. row_sep: Row separator. nil by default. nil means "\r\n or \n". If you want to separate records with \r, give ?\r here.
RETURNS
parsed_cells: num of parsed cells. idx: index of next parsing location of 'src'.
Archived Comments
1. Georgekic
View Tutorial By: Georgekic at 2017-01-03 14:19:12
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