This code is for check if a character is a integer or not (i think). I'm trying to understand what this means, I mean... each part of that line, checking the GREP man pages, but it's really difficult for me. I found it on the internet. If anyone could explain me the part of the grep... what means each thing put there:
echo $character | grep -Eq '^(\+|-)?[0-9]+$'
Thanks people!!!
分析这个正则表达式：
'^(\+|-)?[0-9]+$'
^ - Line Start
(\+|-)? - Optional + or - sign at start
[0-9]+ - One or more digits
$ - Line End
总体而言，它匹配类似+123or-98765或 just之类的字符串9
这里-E用于扩展正则表达式支持，-q用于 grep 命令中的安静。
PS：顺便说一句，您不需要grep进行此检查，可以直接在纯 bash 中执行此操作：
re='^(\+|-)?[0-9]+$'
[[ "$character" =~ $re ]] && echo "its an integer"
我喜欢正则表达式的备忘单：http:
//www.cheatography.com/davechild/cheat-sheets/regular-expressions/
非常有用，你可以轻松分析
'^(+|-)?[0-9]+$'
作为
所以它接受如下：-312353243 或 +1243 或 5678
但不接受：3 456 或 6.789 或 56$（作为美元符号）。