Counting and Calculating with Vim

I was working with a particularly unfriendly SQL dump file which was raising errors indicating that my data had the wrong amount of columns. To figure out what was going on, I used Vim to count the number of columns and then corrected the data using a substitution command.

To count the number of columns, I used %s/,//gn. The n flag causes :substitute to return the number of matches without actually performing any changes. The data itself had columns separated by commas, so all I needed to search for was a single comma. For more on flags, see :help :s_flags.

The results are displayed at the bottom of the screen, and read 12 matches on 1 lini— in the screenshot I've used s/,//gn instead of %s.

I also find myself regularly needing to increment or decrement numbers in Vim. This crops up when I’m working with array indexes, or sequential IDs from a database. When in Normal mode, the CTRL-A command will increment the number under the cursor, and CTRL-X will decrement it. These commands accept a [count] argument, so if you type 4 CTRL-A Vim should add 4 to the number under the cursor. Be careful if you're using tmux or screen -- in those cases you should able to type CTRL-A a.

If you need to perform quick calculations, you can use the expression register. While in Insert mode, type CTRL-R = and the cursor will turn into a double quote ("). Whatever you type next will be evaluated as an expression, and this includes basic calculations. The prompt isn't specifically for equations, it's Vim script. For more on CTRL-R, see :help i_CTRL-R, and for more on expressions see :help expression-syntax.