When managing files on macOS, you might often need to batch rename multiple files, such as changing their extensions. While there are various ways to do this, using Zsh (Z Shell) is one of the most efficient, especially with the built-in zmv function.

In this post, I'll guide you through using the zmv command to change file extensions in bulk, such as converting .txt files to .text extensions. The command is simple once you get it set up and will save you a lot of time compared to renaming files individually.

Prerequisites

First, ensure that you're using Zsh, as zmv is a Zsh-specific function. Fortunately, macOS has used Zsh as the default shell since macOS Catalina, so you're likely already in the right environment. If you're using an older version of macOS, you can switch to Zsh by running this command:

chsh -s /bin/zsh

Now, you can proceed to work with the zmv command.

Step 1: Enabling zmv

The zmv function isn't available by default, but you can load it by running the following command in your terminal:

autoload -U zmv

This loads the zmv command into your session, allowing you to use it for renaming files.

Feel free to add this to your .zshrc file to load zmv automatically whenever you open a new terminal session.

Step 2: Understanding the Command

The syntax for renaming files with zmv is straightforward. Here's the command we'll be using to change .txt files to .text files:

zmv '(*).txt' '$1.text'

• zmv: The command to perform a batch rename.
• '(*).txt': This part matches any file with the .txt extension. The (*) captures the file's name before the .txt extension.
• '$1.text': This is the target filename format. $1 refers to the part captured by (*) (i.e., the original file name without the extension), and .text is the new extension that we want to assign.

Step 3: Running the Command

Once you've loaded the zmv function and you understand the command syntax, navigate to the directory where your .txt files are located. You can do this using the cd command. For example:

cd /path/to/your/files

Now, run the zmv command:

zmv '(*).txt' '$1.text'

This will rename all .txt files in the current directory to have the .text extension instead.

Step 4: Confirming the Changes

To verify that the files have been renamed correctly, you can list the files in the directory:

ls

You should now see that all .txt files have been renamed to .text.

A Note on Safety

If you're concerned about making a mistake or overwriting existing files, you can run zmv in a "dry-run" mode first. This mode simulates the renaming without actually making any changes. To do this, use the n flag:

zmv -n '(*).txt' '$1.text'

This will show you the changes that would be made, allowing you to confirm everything is as expected before running the actual command.

Conclusion

Batch renaming file extensions on macOS with Zsh's zmv function is a powerful and efficient tool. With a single line of code, you can transform a whole directory of file extensions. Just remember to load the zmv function using autoload -U zmv, and you're good to go!

Now, no more manual renaming! Enjoy the power of automation and get more done with less effort.