sqfstar:tldr:70daf

This command is a shell command that performs two operations using two different utilities: zstdcat and sqfstar. Let's break it down into its components:

1. ${archive-tar-zst}: This is a placeholder for a variable named archive-tar-zst. The value of this variable should be a path to a file in the zstd compressed tar (tar.zst) format.

2. zstdcat: zstdcat is a utility program that reads a compressed file and writes the decompressed content to the standard output. In this case, ${archive-tar-zst} is passed to zstdcat as an input file.

3. |: This is a pipe symbol, used to redirect the standard output of one command (zstdcat) to the standard input of another command (sqfstar).

4. sqfstar: sqfstar is another utility program that treats the standard input as a stream of data and creates a squashfs filesystem using that data. It takes two arguments:

   • ${filesystem-squashfs}: This is a placeholder for a variable named filesystem-squashfs. It should be the desired path for the output squashfs filesystem file.
   • "${*-gz}": The ${*-gz} syntax is a placeholder for all command-line arguments passed to the original shell script or command. It is a mechanism to pass multiple arguments. In this case, the arguments are passed to sqfstar which may use those arguments during the creation of the squashfs filesystem.

So, effectively, this command decompresses the zstd compressed tar file ${archive-tar-zst} using zstdcat, and then pipes the output to sqfstar to create a squashfs filesystem at ${filesystem-squashfs} using any additional command-line arguments provided.