Some useful commands to work with vi
| i | <td>
insert
</td>
| r | <td>
replace
</td>
| 9yl | <td>
copy nine characters from cursor position, e.g 192.168.1.0 192.168.1 will be copied
</td>
| p | <td>
paste what you have copied
</td>
| x | <td>
delete character
</td>
| :wq | <td>
write and quit (save and close)
</td>
| /search_string | <td>
find search_string
</td>
| n | <td>
go to next occurrence of search_string
</td>
| N | <td>
go to previous occurrence of search_string
</td>
| dd | <td>
delete line
</td>
| 10dd | <td>
delete next 10 lines
</td>
| yy | <td>
copy line
</td>
| 10yy | <td>
copy next 10 lines
</td>
| r | <td>
replace current character at cursor
</td>
| R | <td>
replace current word at cursor
</td>