测试变量是否为整数 [英] Testing if a variable is an integer

问题描述

我想测试变量$var是否实际上是整数.我该怎么做?

I would like to test if my variable $var is actually an integer or not. How can I please do that?

推荐答案

只要您使用的bash版本> = 3，就可以使用正则表达式:

As long as you're using bash version >=3 you can use a regular expression:

[[ $a =~ ^-?[0-9]+$ ]] && echo integer

此bash FAQ 提到了各种bash 3.x中bash regex实现中的不一致之处( 是否应使用正则表达式)，在这种情况下，我认为在任何版本中都没有需要引用的字符，因此我们很安全.至少它对我有用:

While this bash FAQ mentions inconsistencies in the bash regex implementation in various bash 3.x (should the regex be quoted or not), I think in this case, there are no characters that need quoting in any version, so we are safe. At least it works for me in:

• 3.00.15(1)-发行版(x86_64-redhat-linux-gnu)
• 3.2.48(1)-发行版(x86_64-apple-darwin12)
• 4.2.25(1)-发行版(x86_64-pc-linux-gnu)

$ a=""
$ [[ $a =~ ^-?[0-9]+$ ]] && echo integer
$ a=" "
$ [[ $a =~ ^-?[0-9]+$ ]] && echo integer
$ a="a"
$ [[ $a =~ ^-?[0-9]+$ ]] && echo integer
$ a='hello world!'
$ [[ $a =~ ^-?[0-9]+$ ]] && echo integer
$ a='hello world 42!'
$ [[ $a =~ ^-?[0-9]+$ ]] && echo integer
$ a="42"
$ [[ $a =~ ^-?[0-9]+$ ]] && echo integer
integer
$ a="42.1"
$ [[ $a =~ ^-?[0-9]+$ ]] && echo integer
$ a="-42"
$ [[ $a =~ ^-?[0-9]+$ ]] && echo integer
integer
$ a="two"
$ [[ $a =~ ^-?[0-9]+$ ]] && echo integer

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