How to open Filtered VIM file without overwriting current text

Question

I have a file in VIM with a bunch of names on separate lines.

I want to open this file with filtered results (easier to view). BUT, I want to preserve the other lines/names.

Example:

#open names file only show names that begin with a
vim names.txt | grep “a.*” 

I know the above won’t work but hypothetically speaking if it were to open with the desired functionality (displaying only names starting with a) and I then made changes to those name, and finally saved the file.

I would like to open the file normally without grep and see the rest of the names unaffected.

What I tried…

 cat names.txt | grep “a.*” > names.txt

Unfortunately this does not work because it will overwrite the current names.txt file once i run :wq in vim.

Any and all help / suggestions are appreciated

Clarifying the use case The intention is to take each name in a file filter it with a specific pattern. Make changes to those matches and then save the file. So I want to edit all the names that match “^ab”. I’ll make a change to the name. The reason for filtering is for visuals but also to more easily apply macros. Also some tasks are easier since VIM does not support non-continuous highlighting.

The file will have changes - those names that matched the pattern for the filter. But, I want those names that were not matches to remain original.

Answer 1

Your actual use case is not super clear.

Do you want to edit the filtered lines without affecting the original file?

From within Vim

If the file is already loaded in Vim, you can do :g/foo to list the lines matching your pattern at the bottom of the screen until you press a key.

Another method consists in putting the content of the file in a new buffer and then filtering it:

:vnew | r# | v/foo/d

which should leave you with two windows, one with the original file and one with the filtered lines.

From your shell

If your shell supports process substitution, you can do:

$ vim <(grep foo filename)

where the output of grep foo filename is presented to Vim as a "file".

Do you want to navigate between the matching lines without affecting the original content?

From within Vim

Simply use :help :vimgrep and :help quickfix:

:vimgrep foo | cwindow

From your shell

You can tell Vim to use the content of a "file" to build a quickfix list with the -q flag and execute an arbitrary command afterward with the + flag:

$ vim -q <(grep -nH foo filename) +cwindow

See :help -q and :help -+c.