awkでCSVに空の列を挿入します
example.csv
1,tokyo,100,200,300
2,saitama,100,200,300
3,kanagawa,100,200,300
4,chiba,100,200,300
5,ibaraki,100,200,300
command
３列目と4列目の間に、空の列を入れて、別ファイルとして書き出す
cat example.csv | awk -F"," {print $1 "," $2 "," $3 "," "," $4 "," $5} > test.csv
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