How to calculate days between two dates using bash 怎麼計算兩個日期中間有幾天

 How to calculate days between two dates using bash 怎麼計算兩個日期中間有幾天

 echo $((($(date -d "2021-04-26" +%s)-$(date -d "2021-01-01" +%s))/86400))

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 echo $((($(date +%s -d 20210426)-$(date +%s -d 20210101))/86000))

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