rustup does things that take a long time before quick and easy things that can fail

[db48x]

 db48x  ~  sh rustup.sh 
info: downloading installer
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 9500k  100 9500k    0     0  14744      0  0:10:59  0:10:59 --:--:-- 33938
warning: it looks like you have existing multirust metadata
warning: rustup cannot be installed alongside multirust
warning: delete `/home/db48x/.multirust` before installing rustup
error: cannot install while multirust is installed
rustup: command failed: /tmp/tmp.FDRmWtDAD3/rustup-init

Much better to fail early. Doesn't help either that it deleted the temporary directory. BTW, have you thought about making an rpm/deb instead of reinventing the wheel?

[db48x]

 db48x  ~  sh rustup.sh 
info: downloading installer
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 9500k  100 9500k    0     0  20358      0  0:07:57  0:07:57 --:--:-- 36882
warning: it looks like you have an existing installation of Rust
warning: rustup cannot be installed alongside Rust. Please uninstall first
warning: run `/usr/local/lib/rustlib/uninstall.sh` as root to uninstall Rust
error: cannot install while Rust is installed
rustup: command failed: /tmp/tmp.xaa80Prw74/rustup-init

/me sighs