Question

Is there a way to programmatically write on the bar below vim windows? I’m referring to the bar which displays the filename, cursor row + column, and the percentage of the document above the bottom of the window.

Answer 1

It is called the status line.

You can get more information by typing :help statusline.

This is the one I used which includes line and column at the bottom right.

set statusline=%f%m%r%h\ [%L]\ [%{&ff}]\ %y%=[%p%%]\ [line:%05l,col:%02v]   
                │ │ │ │    │       │      │    │           │       │  
                │ │ │ │    │       │      │    │           │       └─ column number  
                │ │ │ │    │       │      │    │           └─── line number  
                │ │ │ │    │       │      │    └── percentage in file  
                │ │ │ │    │       │      └── file type  
                │ │ │ │    │       └── file format (dos/unix)  
                │ │ │ │    └── total number of line in file  
                │ │ │ └── help flag  
                │ │ └── read only flag  
                │ └── modified flag : [+] if modified, [-] if not modifiable  
                └── relative`  

The rendering is not ideal but the options, which are starting with the %sign, are described from left to right as you go down. They are all described in help.

This is a pretty static configuration, if you are willing to use a vim-plugin, there are some like vim-airline that provides more advanced features like git integration.