zdiff:tldr:27a4b

The command "zdiff ${filename}" is used to compare the contents of compressed files. Here's how it works:

1. "zdiff" is a command-line utility in Unix-like operating systems, used to compare compressed files. It is typically used with files that are compressed using the gzip format (.gz extension).

2. "${filename}" is a placeholder for the name of the compressed file that you want to compare. You need to replace "${filename}" with the actual name of the file.

3. When you run the command, it will compare the compressed file specified with the previous version of the file (if any). It will then display the differences between the two files, if any exist.

4. The comparison takes place by decompressing both files in a temporary location and then comparing the uncompressed content. The original compressed files themselves are not modified.

5. The command will output the differences between the files in a human-readable format, showing the specific lines or sections that differ.

This command can be helpful when you want to verify if the contents of a compressed file have changed compared to a previous version or to compare two versions of a compressed file.