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tac:tldr:504c4
The "tac" command is a Unix/Linux command that is used to concatenate and display files in reverse order. It takes input from specified files or standard input and displays the lines of each file in reverse order, starting with the last line.
In the given command, "--before" is not a valid option for the "tac" command. However, assuming it is a placeholder, the command would concatenate and display the content of files "${filename1}", "${filename2}", and so on, in reverse order. The "--before" part would need to be replaced with a valid option or removed if unnecessary.
Here's a more correct example of using the "tac" command with filenames: tac file1.txt file2.txt
This command will display the content of "file1.txt" and "file2.txt" concatenated in reverse order.