-z 在 Bash 中是什麼意思？ [複製] - What does -z mean in Bash? [duplicate]

問題：

This question already has answers here : 這個問題在這裏已經有了答案：

List of 'if' switches anywhere? 任何地方的“if”開關列表？ (5 answers) (5 個回答)

Closed 4 years ago . 4年前關閉。

I'm looking at the following code:我正在查看以下代碼：

if [ -z $2 ]; then
        echo "usage: ...

(The 3 dots are irrelevant usage details.) （這 3 個點是不相關的使用細節。）
Maybe I'm googling it wrong, but I couldn't find an explanation for the -z option.也許我在谷歌上搜索錯了，但我找不到-z選項的解釋。

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解決方案：

參考一： https://en.stackoom.com/question/1Dvlm
參考二： https://stackoom.com/question/1Dvlm