add nix command flakes examples

prezentace.md

@@ -38,9 +38,9 @@ footer: "Albert Vala, Filip Kohout, Nix flakes & Nix command"
 # Porovnani
 
 ```shell
-nix-shell -p cowsay #Stare
-nix shell nixpkgs#cowsay #Nove
-nix run nixpkgs#cowsay #Nove
+nix-shell -p cowsay #Old
+nix shell nixpkgs#cowsay #New
+nix run nixpkgs#cowsay #New
 ```
 
 ---
@@ -68,6 +68,17 @@ nix run nixpkgs#cowsay #Nove
 
 * Cokoliv.
 
+---
+# Nix command + flakes
+- temp shell
+```shell
+nix shell nixpkgs#alejandra
+nix shell github:kamadorueda/alejandra
+```
+- Show output attr
+```shell
+nix flake show github:kamadorueda/alejandra
+``` 
 ---
 
 # Jak pouzit flakes na system configuraci?
@@ -167,8 +178,8 @@ nh os switch
 ```
 
 ```shell
-nix build /etc/nixos#nixosConfigurations.nixos.config.system.build.toplevel \
-&& ./result/bin/switch-to-configuration switch
+nix build /etc/nixos#nixosConfigurations.nixos.config.system.build.toplevel
+./result/bin/switch-to-configuration switch
 ```
 
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