Question: I am generating a regular expression that can contain any *letters* or numbers or an underscore `[a-zA-Z0-9_]` but not contain words that exactly match `log`, `login` and lastly `test`.

Can anybody help me with this?

Answer: 
```
 ^(?!(^test$)|(^log$)|(^login$))([A-Za-z0-9_-/]+)$ 

```

Did the trick for me. Thanks for your answers guys
I think the below regular expression should do the trick

```
^((?!log|login|test)[a-zA-Z0-9_])*$

```