nvram:tldr:abe7d

The command "sudo nvram -xf ${filename-xml}" is used to set NVRAM variables on a Unix or Unix-like system using the NVRAM utility. Let's break it down:

1. "sudo" is a command used to run a command with superuser or root privileges. It is used when an operation requires administrative access.

2. "nvram" is a utility that allows manipulation of firmware NVRAM (non-volatile random-access memory) variables. NVRAM is a small amount of memory that stores system firmware settings and variables.

3. "-xf" are command options that modify the behavior of the nvram command.

   • "-x" specifies that the NVRAM variables will be set using a text file.
   • "-f" is used to specify the input file that contains the values for the variables.

4. "${filename-xml}" represents a substitution variable. It is used to substitute the value of the environment variable "filename-xml". The value of this variable should be the name of an XML file that contains the NVRAM variables and their values.

So, when the command is executed, it will read the XML file specified by the "filename-xml" variable and set the NVRAM variables according to the values specified in the XML file. The "sudo" command is used to ensure that the operation has sufficient privileges.