BASH：字符串测试是否有效作为整数？ [英] BASH: Test whether string is valid as an integer?

问题描述

我试图做的共同之处就够了：在shell脚本解析用户输入。如果用户提供了一个有效的整数，剧本做一件事情，如果没有有效的，但它确实别的东西。麻烦的是，我还没有发现这样做的一个简单的（和合理的优雅的）的方式 - 我不希望有成炭挑它除了字符

我知道这一定是容易的，但我不知道怎么办。我能做到这一点的十几种语言，但不是BASH！

在我的研究，我发现这一点：

<一个href=\"http://stackoverflow.com/questions/136146/regular-ex$p$pssion-to-test-whether-a-string-consists-of-a-valid-real-number-in-ba\">http://stackoverflow.com/questions/136146/regular-ex$p$pssion-to-test-whether-a-string-consists-of-a-valid-real-number-in-ba

和有一个其中的答案谈到有关正则表达式，但到目前为止我所知，这是在C语言中（等等）的功能。尽管如此，它有什么看起来像一个伟大的答案，所以我使用grep尝试过，但grep的不知道该怎么办。我想这-P在我的箱子是指把它当作一个正则表达式PERL - 虚无缥缈。短跑E（-E）也不能工作。而且也没有-F。

只是要清楚，我想这样的事情，寻找任何输出 - 在那里，我就砍了脚本利用不管我得到的。 （IOW，我期待，当一个有效的行被重复不符合要求的输入返回任何内容。）

 天翻地覆= $（回声$ 2| grep的-E/ ^ [ -  +]（：\\ [0-9] + |（？：？？0 | [ 1-9] [0-9] *）（？：\\？[0-9] *））$ /）
如果[-z$天翻地覆];
然后
   回声不是一个整数 - 没有来自grep的背
其他
   回声整数。
科幻
 

会有人请说明如何，这是最容易做的？

坦率地说，这是一个短期的未来试验，在我看来。它应该有一个这样的标志

 如果[-I字符串];
然后
   回声字符串是一个有效的整数。
其他
   回声字符串不是有效的整数。
科幻
 

感谢。

解决方案

  [$ VAR =〜^  - ？[0-9] + $]
 

I'm trying to do something common enough: Parse user input in a shell script. If the user provided a valid integer, the script does one thing, and if not valid, it does something else. Trouble is, I haven't found an easy (and reasonably elegant) way of doing this - I don't want to have to pick it apart char by char.

I know this must be easy but I don't know how. I could do it in a dozen languages, but not BASH!

In my research I found this:

http://stackoverflow.com/questions/136146/regular-expression-to-test-whether-a-string-consists-of-a-valid-real-number-in-ba

And there's an answer therein that talks about regex, but so far as I know, that's a function available in C (among others). Still, it had what looked like a great answer so I tried it with grep, but grep didn't know what to do with it. I tried -P which on my box means to treat it as a PERL regexp - nada. Dash E (-E) didn't work either. And neither did -F.

Just to be clear, I'm trying something like this, looking for any output - from there, I'll hack up the script to take advantage of whatever I get. (IOW, I was expecting that a non-conforming input returns nothing while a valid line gets repeated.)

snafu=$(echo "$2" | grep -E "/^[-+]?(?:\.[0-9]+|(?:0|[1-9][0-9]*)(?:\.[0-9]*)?)$/")
if [ -z "$snafu" ] ;
then
   echo "Not an integer - nothing back from the grep"
else
   echo "Integer."
fi

Would someone please illustrate how this is most easily done?

Frankly, this is a short-coming of TEST, in my opinion. It should have a flag like this

if [ -I "string" ] ;
then
   echo "String is a valid integer."
else
   echo "String is not a valid integer."
fi

Thanks.

解决方案

[[ $var =~ ^-?[0-9]+$ ]]

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