nix-build:tldr:a17e6

This command is using the Nix package manager to build the Firefox package from the specified nixpkgs repository.

Here is the breakdown:

• nix-build is the command used to build Nix packages.
• <nixpkgs> is a placeholder representing a specific Nix package repository. It should be replaced with the path to the actual nixpkgs repository.
• --attr ${firefox} specifies the attribute of the package to build. In this case, it is using the value of the ${firefox} variable, which is likely defined earlier in the script or shell environment. The ${firefox} variable determines which version or variant of Firefox to build. It could be a specific version, a specific variant like firefox-esr, or any other valid attribute name for the Firefox package defined in the nixpkgs repository.

Overall, this command will build the Firefox package using the specified nixpkgs repository, with the version or variant specified by the ${firefox} variable.