Substring of filename in external command (bang)

Question

Is it possible to execute bash string manipulations to the filename of the current file, represented by % in external commands from within vim?

Example:

I am editing a file myfile.txt. Using :! command %, I can execute a command on myfile.txt from within vim. For instance, to copy myfile.txt to myfile.ext (simply change the extension), I can write :! cp % myfile.ext. But there is some redundancy, and I'd like to deduce myfile.ext from % (and avoid writing myfile).

In bash, if the name myfile.txt is contained in the variable $var, I can write cp $var ${var%txt}ext for instance.

Is there a way to mimick this in vim? Of course, I cannot write :! cp % ${%%txt}ext... though it is what I'd like to be able to!

Answer 1

You don't need to shell out to save a copy with a different extension. Try either of the following, both of which use the "root" :r modifier to strip the extension from the filename:

:w %:r.ext
:sav %:r.ext

The former will save a copy, but leave you editing the original. The latter will switch over so that you are now editing the copy.

See :h filename-modifiers for details of the many different modifiers Vim provides.