mmv:tldr:8311f

The command you provided is using the mmv utility with some options and arguments. mmv stands for "mass move" and it is used to rename multiple files simultaneously.

Here is an explanation of the command:

• mmv: This is the name of the utility that is being executed.
• -a: This option tells mmv to enable auto-renaming mode. In this mode, mmv will automatically rename files without prompting for confirmation.
• "${*-txt}": This is a substitution expression that expands to all the command line arguments (filenames) passed to the script, appended with "-txt". For example, if the command is executed like this: mmv -a file1 file2, then "${*-txt}" will expand to "file1-txt file2-txt". This is specifying the current filenames to be renamed.
• "${all-txt}": This is another substitution expression but without *. Instead, it is replacing all filenames with the string "all-txt". So, in this case, if executed like: mmv -a file1 file2, then "${all-txt}" will expand to "all-txt". This is specifying the new filenames to be renamed.

To summarize, the command is using mmv to automatically rename the specified list of files. It appends "-txt" to the current filenames and replaces them with "all-txt".