比较shell脚本中的两个日期 [英] Compare two dates in shell script

问题描述

我需要比较存储在两个变量中的两个日期，格式为 YYYY-MM-DD .我想我可以将它们存储在另一个变量中，并使用一些 tr -d-" ，然后像整数一样进行比较，但是我不知道该怎么做.预先感谢！

I need to compare two dates which are stored in two variables, the format is YYYY-MM-DD . I suppose I can store them in another variables and use some tr -d "-",then compare like integers, but I don’t know how. Thanks in advance !

推荐答案

您可能需要调出 expr ，具体取决于您的神秘外壳:

You may need to call out to expr, depending on your mystery shell:

d1="2015-03-31" d2="2015-04-01"
if [ "$d1" = "$d2" ]; then
    echo "same day"
elif expr "$d1" "<" "$d2" >/dev/null; then
    echo "d1 is earlier than d2"
else
    echo "d1 is later than d2"
fi

d1 is earlier than d2

---

test 命令(或别名 [))仅实现字符串相等和不相等运算符.当您给(非bash)shell发出此命令时:

---

The test command (or it's alias [) only implements string equality and inequality operators. When you give the (non-bash) shell this command:

[ "$d1" > "$d2" ]

>"$ d2" 部分被视为stdout重定向.创建名为(在本例中)"2015-04-01"的零长度文件，条件命令变为

the > "$d2" part is treated as stdout redirection. A zero-length file named (in this case) "2015-04-01" is created, and the conditional command becomes

[ "$d1" ]

并且由于该变量为非空变量，因此评估为成功状态.

and as the variable is non-empty, that evaluates to a success status.

该文件的大小为零，因为 [命令没有标准输出.

The file is zero size because the [ command generates no standard output.

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