如何在Bash中比较字符串 [英] How to compare strings in Bash

问题描述

如何将变量与字符串进行比较(如果匹配则执行某些操作)?

How do I compare a variable to a string (and do something if they match)?

推荐答案

在if语句中使用变量

if [ "$x" = "valid" ]; then
  echo "x has the value 'valid'"
fi

如果您想在它们不匹配时执行某些操作，请将=替换为!=.您可以阅读有关字符串操作和<在各自文档中的href ="http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO-11.html#ss11.3" rel ="noreferrer">算术运算.

If you want to do something when they don't match, replace = with !=. You can read more about string operations and arithmetic operations in their respective documentation.

您希望在$x周围加上引号，因为如果它为空，则您的Bash脚本会遇到语法错误，如下所示:

You want the quotes around $x, because if it is empty, your Bash script encounters a syntax error as seen below:

if [ = "valid" ]; then

---

==运算符的非标准用法

请注意，Bash允许==用于与[相等，但是这不是标准.

---

Non-standard use of == operator

Note that Bash allows == to be used for equality with [, but this is not standard.

使用第一种情况，其中$x周围的引号是可选的:

Use either the first case wherein the quotes around $x are optional:

if [[ "$x" == "valid" ]]; then

或使用第二种情况:

if [ "$x" = "valid" ]; then

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