How to delete all files except one named file from a specific folder [duplicate]

Here is the situation.

I have a directory which contains many files with different extensions. I want to delete all files except one with a specific name.

This could be easily done using the GUI by selecting all and pressing ctrl and deselecting the file in question.

That is exactly what I want to, but how can I do it from the command line?

For example: dirA contains the following files:

a.txt
b.txt
c.php
d.html
a.db
b.db
e.html

I want to delete all files keeping only the file named a.txt.

I've come with this easy simple great command:

rm !(a.txt)

you can use ! as a negation

Test the glob with echo first i.e.

echo !(a.txt)

If it doesn't work, for bash you may need to enable this with

shopt -s extglob

If you wanted to keep both a.txt and b.txt, you can use !(a.txt|b.txt) or !([ab].txt).

Edit:

to make rm working recursively just add -r like

rm -r !(a.txt)

and also, it is working with folder. just need to change the name to the dir name, such as for a_dir

rm -r !(a_dir)

You can try this command:

find . \! -name 'a.txt' -delete

But you need be careful because find command is recursive.

You can do this in terminal:

cd dirA 
export GLOBIGNORE=a.txt
rm *
export GLOBIGNORE=

You can use the command :

find ! -name 'a.txt' -type f -exec rm -f {} +

This will look for files (-type f) in the current directory except for file a.txt (! -name 'a.txt) and then will remove them (-exec rm -f {} +)