Is it possible to use regex for matching with a condition?

Question

I posted this question on super user and I was suggested to post this question on stackoverflow.

I really like vim and today I faced with the intresting problem and I think it can be done via regexp but I can't form out proper one.

I've got a very big sql-file. It consolidates many different queries. File has content with something like this:

select * from hr.employees, oe.orders, oe.order_items
select * from hr.employess, oe.orders, hr.job_history
select * from oe.customers, oe.orders, hr.employees
select * from hr.employees, hr.departments, hr.locations

How can I select only that lines, which has only one match with hr. on the line?. For example above it will be first and third lines.

Answer 1

Sure, it is possible to match such lines. This pattern matches:

^\%(\%(hr\.\)\@!.\)*hr\.\%(\%(hr\.\)\@!.\)*$

Some people like to reduce the amount of backslash-escaping by using the very magic switch \v. Then the same pattern becomes

\v^%(%(hr\.)@!.)*hr\.%(%(hr\.)@!.)*$

(Here I used non-capturing parentheses \%(...\) but capturing parentheses \(...\) would work just as well.)

The question is: What do you want to do with these lines? Delete them?

In that case you could use the :global command:

:g/\v^%(%(hr\.)@!.)*hr\.%(%(hr\.)@!.)*$/d

More information at

• :h :global
• :h /\v
• :h /\%(
• :h /\@!

Answer 2

To check if line contains only single occurrence of hr. use regex pattern

^(?=.*\bhr\.)(?!.*\bhr\..*\bhr\.).* with m modifier. I suggest to use grep -P utility.