I understand that grep can extract the specific content from a file line by line. 
Just wondering how can add another column before or after each line as an index. 
For example: 

```
grep "aaa"  text.txt > tmp.txt

```

In the tmp.txt file, we can see the content as follows, 

```
aaawekjre
qejrteraaa
wrgeaaaere

```

However, I would like to add a specific index as an extra column. 
Therefore, the tmp.txt might look like this:

```
John aaawekjre
John qejrteraaa
John wrgeaaaere

```