bash - 如何在 BASH 中的 IF THEN 条件测试中添加 OR？

Question

我有这样的条件：

if [ "$day" == "1" ]
then
    echo "First day."
fi

我想添加一个额外的条件，以便如果其中一个为真，它将打印“第一天”，例如：

IF $day IS 1 OR $a IS 1
THEN
    "First day."
FI

这如何在 BASH 中完成？

Answer 1

保持 POSIX 兼容性，有两种选择：

if [ "$day" = "1" ] || [ "$a" = "1" ]; then ... fi

if [ "$day" = "1" -o "$a" = "1" ]; then ... fi

在 bash 中，有两个附加选项：

if [[ $day = 1 || $a = 1 ]]; then ... fi

if (( day == 1 || a == 1 )); then ... fi

Answer 2

if [ "$day" == "1" ] || [ "$a" == "1" ]; then echo "First day."; fi

或者

if [ "$day" == "1" ] || [ “$a" == "1" ]
then
    echo "First day."
fi

Answer 3

使用-o（逻辑或）：

if [ "$day" == "1" -o "$a" == "1" ]
then
    echo "First day."
fi