tac:tldr:3cff7

The command "tac --separator ${,} ${filename1 filename2 ---}" is used to reverse the order of lines in one or multiple files, while also specifying a custom separator.

Here's an explanation of each component in the command:

• tac: It is a command-line utility that stands for "reverse cat". It reads input from files or standard input and prints the output in reverse order.

• --separator ${,}: This specifies the separator used to separate records in the file(s). In this case, the separator is set to a comma ",". The ${,} is a way to represent the literal comma character.

• ${filename1 filename2 ---}: This represents the list of files that you want to reverse the order of. You need to replace filename1 and filename2 with the actual names of the files you want to reverse. The --- (three hyphens) indicates the end of the list of files.

To summarize, the command tac --separator ${,} ${filename1 filename2 ---} will reverse the order of lines in the specified files, with the separator between records set to a comma.