Can't delete read-only file on Mac after disabling SIP

Question

I want to have different versions of ruby, i am using asdf for it. So, i have installed some different versions of ruby, but i can not switch their, because(maybe) i have /usr/bin/ruby

d@mac ~ % asdf list
ruby
  2.5.1
  2.6.2
sd@mac ~ % asdf global ruby 2.5.1
sd@mac ~ % ruby -v
ruby 2.6.8p205 (2021-07-07 revision 67951) [universal.arm64e-darwin21]
sd@mac ~ % which ruby
/usr/bin/ruby
sd@mac ~ % whereis ruby
ruby: /usr/bin/ruby /usr/share/man/man1/ruby.1
sd@mac ~ % asdf reshim ruby
sd@mac ~ % ruby -v
ruby 2.6.8p205 (2021-07-07 revision 67951) [universal.arm64e-darwin21]
sd@mac ~ % asdf exec ruby -v
ruby 2.5.1p57 (2018-03-29 revision 63029) [-darwin21]

I have a problem when trying to delete a read-only file. I have disabled SIP with csrutil, but there's still problem:

sd@mac ~ % ls -la /usr/bin | grep ruby
-r-xr-xr-x     1 root   wheel    167888 Mar 26 09:21 ruby
sd@mac ~ % sudo rm -rf /usr/bin/ruby
Password:
rm: /usr/bin/ruby: Read-only file system
sd@mac ~ % sudo chmod 777 /usr/bin/ruby
chmod: Unable to change file mode on /usr/bin/ruby: Read-only file system

How I can delete /usr/bin/ruby for switching ruby versions?

Answer 1

I have solved problem with env variable ASDF_RUBY_VERSION

ruby -v 
=> ruby 3.2.2

ASDF_RUBY_VERSION=3.2.1 ruby -v 
=> ruby 3.2.1

It is not problem for me, because i have file .envrc for each project, and i am using utility direnv for auto define env vars

Answer 2

The real answer is that you can't delete the version of ruby that (still) comes with macOS.

You have to use other methods to ensure that the desired version is being used.