「3-3-2.複数のファイルをまとめて、1つのファイルにする」とは逆に1つの入力ファイルから複数の出力ファイルに振り分ける方法について解説します。ここでは、日本郵政公社（2003年3月までは郵政事業庁）が提供している郵便番号データを都道府県別に出力する方法を例にとって説明します。郵便番号データは下記のサイトにあるので参照してください。
http://www.post.japanpost.jp/zipcode/
入力データの1項目目はJISで定められた都道府県コード（2バイト）と市区町村コード（3バイト）の2つを組み合わせた5バイトのデータになっています。そこで、入力データの1項目目から先頭2バイトを取り、そのデータに基づいて、出力ファイルを分けて出力します。
具体的には、【スクリプト】その１を見ていただければわかるように、Rubyでは、ioクラスのオブジェクトに変数を指定することはできませんが、openメソッドの引数で指定するファイル名には変数が指定できますので、入力データの1つとして、県別の出力ファイル名を指定したファイルをあらかじめ用意しておくことで、スクリプト自体がすっきりとした形になります。openメソッドを定数で指定した場合、どのようになるかを【スクリプト】その２で提示していますので、比較すると、どのくらい簡潔になるかがわかるでしょう。入出力ファイルが増えてきた場合、このように変数で指定することでスクリプトがすっきりと表示できるようになります。
なお、入力データはキー順に並べ替えてあることが前提となっています。Rubyを利用して並べ替えを行う場合については、[2-4.ソート(並べ替え)処理]を参照してください。
01101,"060 ","0600000","ホッカイドウ","サッポロシチュウオウク","イカニケイサイガナイバアイ","北海道","札幌市中央区","以下に掲載がない場合",0,0,0,0,0,0 01101,"064 ","0640941","ホッカイドウ","サッポロシチュウオウク","アサヒガオカ","北海道","札幌市中央区","旭ケ丘",0,0,1,0,0,0
01,01HOKKAIDO.CSV
02,02AOMORI.CSV
03,03IWATE.CSV
04,04MIYAGI.CSV
05,05AKITA.CSV
06,06YAMAGATA.CSV
07,07FUKUSHIMA.CSV
08,08IBARAKI.CSV
09,09TOCHIGI.CSV
10,10GUMMA.CSV
11,11SAITAMA.CSV
12,12CHIBA.CSV
13,13TOKYO.CSV
14,14KANAGAWA.CSV
15,15NIIGATA.CSV
16,16TOYAMA.CSV
17,17ISHIKAWA.CSV
18,18FUKUI.CSV
19,19YAMANASHI.CSV
20,20NAGANO.CSV
21,21GIFU.CSV
22,22SHIZUOKA.CSV
23,23AICHI.CSV
24,24MIE.CSV
25,25SHIGA.CSV
26,26KYOTO.CSV
27,27OSAKA.CSV
28,28HYOGO.CSV
29,29NARA.CSV
30,30WAKAYAMA.CSV
31,31TOTTORI.CSV
32,32SHIMANE.CSV
33,33OKAYAMA.CSV
34,34HIROSHIMA.CSV
35,35YAMAGUCHI.CSV
36,36TOKUSHIMA.CSV
37,37KAGAWA.CSV
38,38EHIME.CSV
39,39KOCHI.CSV
40,40FUKUOKA.CSV
41,41SAGA.CSV
42,42NAGASAKI.CSV
43,43KUMAMOTO.CSV
44,44OITA.CSV
45,45MIYAZAKI.CSV
46,46KAGOSHIMA.CSV
47,47OKINAWA.CSV
# ken1.rb
# 内容 : 郵便番号データを県別に分割するスクリプト
# Copyright (c) 2002-2015 Mitsuo Minagawa, All rights reserved.
# (minagawa@fb3.so-net.ne.jp)
# 使用方法 : c:\>ruby ken1.rb
#
# 入力ファイル(郵便番号データ)
in1_file = open("ken_all.csv","r")
# 入力ファイル(都道府県名データ)
in2_file = open("ken.txt","r")
in2_ctr = 0 #入力件数(都道府県名データ)
sv_ken = 0 #都道府県コードの保存コード
w_file_nm = Array.new() #都道府県名の配列
# 都道府県名のファイルを読み込む
while (line2 = in2_file.gets)
line2.chomp!
in2 = line2.split(",",-1)
in2_ctr += 1
w_file_nm[in2_ctr] = in2[1]
end
# 主処理
while (line1 = in1_file.gets)
line1.chomp!
# CSV形式のファイルを配列に格納する
in1 = (line1 + ',')
.scan(/"([^"\\]*(?:\\.[^"\\]*)*)",|([^,]*),/)
.collect{|x,y| y || x.gsub(/\\(.)/, '\1')}
w_ken = in1[0].slice(0,2).to_i
if (w_ken != sv_ken)
w_file = w_file_nm[w_ken]
out1_file = open(w_file,"w")
end
# 入力キーを保存
sv_ken = w_ken
# 都道府県別のファイルを出力
out1_file.print line1,"\n"
end
# ファイルのクローズ
in1_file.close
# ken2.rb
# 内容 : 郵便番号データを県別に分割するスクリプト
# Copyright (c) 2002-2015 Mitsuo Minagawa, All rights reserved.
# (minagawa@fb3.so-net.ne.jp)
# 使用方法 : c:\>ruby ken2.rb
#
# 入力ファイル
in1_file = open("ken_all.csv","r")
# 出力ファイル
out01_file = open("01HOKKAIDO.CSV","w")
out02_file = open("02AOMORI.CSV","w")
out03_file = open("03IWATE.CSV","w")
out04_file = open("04MIYAGI.CSV","w")
out05_file = open("05AKITA.CSV","w")
out06_file = open("06YAMAGATA.CSV","w")
out07_file = open("07FUKUSHIMA.CSV","w")
out08_file = open("08IBARAKI.CSV","w")
out09_file = open("09TOCHIGI.CSV","w")
out10_file = open("10GUMMA.CSV","w")
out11_file = open("11SAITAMA.CSV","w")
out12_file = open("12CHIBA.CSV","w")
out13_file = open("13TOKYO.CSV","w")
out14_file = open("14KANAGAWA.CSV","w")
out15_file = open("15NIIGATA.CSV","w")
out16_file = open("16TOYAMA.CSV","w")
out17_file = open("17ISHIKAWA.CSV","w")
out18_file = open("18FUKUI.CSV","w")
out19_file = open("19YAMANASHI.CSV","w")
out20_file = open("20NAGANO.CSV","w")
out21_file = open("21GIFU.CSV","w")
out22_file = open("22SHIZUOKA.CSV","w")
out23_file = open("23AICHI.CSV","w")
out24_file = open("24MIE.CSV","w")
out25_file = open("25SHIGA.CSV","w")
out26_file = open("26KYOTO.CSV","w")
out27_file = open("27OSAKA.CSV","w")
out28_file = open("28HYOGO.CSV","w")
out29_file = open("29NARA.CSV","w")
out30_file = open("30WAKAYAMA.CSV","w")
out31_file = open("31TOTTORI.CSV","w")
out32_file = open("32SHIMANE.CSV","w")
out33_file = open("33OKAYAMA.CSV","w")
out34_file = open("34HIROSHIMA.CSV","w")
out35_file = open("35YAMAGUCHI.CSV","w")
out36_file = open("36TOKUSHIMA.CSV","w")
out37_file = open("37KAGAWA.CSV","w")
out38_file = open("38EHIME.CSV","w")
out39_file = open("39KOCHI.CSV","w")
out40_file = open("40FUKUOKA.CSV","w")
out41_file = open("41SAGA.CSV","w")
out42_file = open("42NAGASAKI.CSV","w")
out43_file = open("43KUMAMOTO.CSV","w")
out44_file = open("44OITA.CSV","w")
out45_file = open("45MIYAZAKI.CSV","w")
out46_file = open("46KAGOSHIMA.CSV","w")
out47_file = open("47OKINAWA.CSV","w")
# 主処理
while (line1 = in1_file.gets)
line1.chomp!
# CSV形式のファイルを配列に格納する
in1 = (line1 + ',')
.scan(/"([^"\\]*(?:\\.[^"\\]*)*)",|([^,]*),/)
.collect{|x,y| y || x.gsub(/\\(.)/, '\1')}
w_ken = in1[0].slice(0,2)
case w_ken
when "01"
out01_file.print line1,"\n"
when "02"
out02_file.print line1,"\n"
when "03"
out03_file.print line1,"\n"
when "04"
out04_file.print line1,"\n"
when "05"
out05_file.print line1,"\n"
when "06"
out06_file.print line1,"\n"
when "07"
out07_file.print line1,"\n"
when "08"
out08_file.print line1,"\n"
when "09"
out09_file.print line1,"\n"
when "10"
out10_file.print line1,"\n"
when "11"
out11_file.print line1,"\n"
when "12"
out12_file.print line1,"\n"
when "13"
out13_file.print line1,"\n"
when "14"
out14_file.print line1,"\n"
when "15"
out15_file.print line1,"\n"
when "16"
out16_file.print line1,"\n"
when "17"
out17_file.print line1,"\n"
when "18"
out18_file.print line1,"\n"
when "19"
out19_file.print line1,"\n"
when "20"
out20_file.print line1,"\n"
when "21"
out21_file.print line1,"\n"
when "22"
out22_file.print line1,"\n"
when "23"
out23_file.print line1,"\n"
when "24"
out24_file.print line1,"\n"
when "25"
out25_file.print line1,"\n"
when "26"
out26_file.print line1,"\n"
when "27"
out27_file.print line1,"\n"
when "28"
out28_file.print line1,"\n"
when "29"
out29_file.print line1,"\n"
when "30"
out30_file.print line1,"\n"
when "31"
out31_file.print line1,"\n"
when "32"
out32_file.print line1,"\n"
when "33"
out33_file.print line1,"\n"
when "34"
out34_file.print line1,"\n"
when "35"
out35_file.print line1,"\n"
when "36"
out36_file.print line1,"\n"
when "37"
out37_file.print line1,"\n"
when "38"
out38_file.print line1,"\n"
when "39"
out39_file.print line1,"\n"
when "40"
out40_file.print line1,"\n"
when "41"
out41_file.print line1,"\n"
when "42"
out42_file.print line1,"\n"
when "43"
out43_file.print line1,"\n"
when "44"
out44_file.print line1,"\n"
when "45"
out45_file.print line1,"\n"
when "46"
out46_file.print line1,"\n"
when "47"
out47_file.print line1,"\n"
end
end
# ファイルのクローズ
in1_file.close
out01_file.close
out02_file.close
out03_file.close
out04_file.close
out05_file.close
out06_file.close
out07_file.close
out08_file.close
out09_file.close
out10_file.close
out11_file.close
out12_file.close
out13_file.close
out14_file.close
out15_file.close
out16_file.close
out17_file.close
out18_file.close
out19_file.close
out20_file.close
out21_file.close
out22_file.close
out23_file.close
out24_file.close
out25_file.close
out26_file.close
out27_file.close
out28_file.close
out29_file.close
out30_file.close
out31_file.close
out32_file.close
out33_file.close
out34_file.close
out35_file.close
out36_file.close
out37_file.close
out38_file.close
out39_file.close
out40_file.close
out41_file.close
out42_file.close
out43_file.close
out44_file.close
out45_file.close
out46_file.close
out47_file.close
入力データ(県別の出力ファイル名)のサンプルはこちらにあります。