What is the difference between these two regular expressions?

Question

What is the difference between these two regular expressions :

[a-zA-Z!@#$%^&*()_=;.?]+[0-9]+

and

[a-zA-Z]+[!@#$%^&*()_=;.?][0-9]+

A token can start with multiple alphabetical characters and will end with number sequence . It can also start with one special character and will end with number sequence .

First regex breaks the string jkl3242oij92384nji332332!23#900&6382^832983@7729.979797_70979797 into the desired tokens but second doesn't. Why ?

How do I implement the concept, that only one special character is allowed ?

Answer 1

After I got that right:

([a-zA-Z]+|[!@#$%^&*()_=;.?])[0-9]+

Starts with multiple alphanumerical or one special and ends with digits only.

Regex101

Answer 2

The difference is that regex #1: [a-zA-Z!@#$%^&*()_=;.?]+[0-9]+ will break a string into tokens of at least one of the characters: [a-zA-Z!@#$%^&*()_=;.?] followed by at least on number [0-9] .

Regex #2: [a-zA-Z]+[!@#$%^&*()_=;.?][0-9]+ on the other hand, will break a string into tokens of at least one letter [a-zA-Z] , followed by one of [!@#$%^&*()_=;.?] , followed by at least one number [0-9] .

Answer 3

并不是您问题的真正答案，但是我发现这是调试正则表达式的非常有用的工具： https : //www.debuggex.com/