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文字列の出現回数を調べるawk

SQLでいうところのGROUP BYのようなことをしたい場合。awkで出来たりします。

調べたいファイル
$ cat fruits.list
apple
orange
orange
apple
melon
結果
$ cat fruits.list | awk '{count[$0]++}END{for(i in count)print count[i], i}'
2 apple
1 melon
2 orange

実は unique -c使ったほうが簡単です。

uniq
$ cat fruits.list | sort | uniq -c
      2 apple
      1 melon
      2 orange

fruits.listがめちゃくちゃデカい場合とかにはsortのコストがバカにならないのでawkの方がいいですね

データの件数が多い場合はawkに利点があるようです!

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