How to Specify a Custom Output Filename in Wget?

When downloading files using the wget command-line utility, the tool automatically names the saved file based on the last portion of the URL. However, you can easily override this default behavior and specify a custom output filename by using the -O (uppercase letter O) option. This article provides a quick overview of how to rename files during a download, handle different directory paths, and avoid common syntax pitfalls.

The Basic Syntax for Renaming Downloads

To save a downloaded file under a specific name, append the -O option followed by your desired filename. The basic structure of the command looks like this:

wget -O custom_name.ext "URL"

For example, if you want to download a text file but save it as my_notes.txt, you would run the following command in your terminal:

wget -O my_notes.txt "https://example.com/downloads/file-xyz.txt"

Saving to Specific Directories

The -O option is not limited to just changing the filename; it also accepts absolute or relative directory paths. This allows you to download and move a file to a specific folder in a single step.

• Relative Path: wget -O documents/report.pdf "https://example.com/report"
• Absolute Path: wget -O /home/user/downloads/image.png "https://example.com/img"

If the directories specified in the path do not exist, wget will fail to create the file, so ensure the target folder is already created before running the command.

Key Gotchas and Best Practices

While using the -O flag is straightforward, there are a few important technical behaviors to keep in mind to prevent accidental data loss:

• Case Sensitivity: Always use an uppercase -O. Using a lowercase -o redirects the wget log output to a text file rather than changing the downloaded file’s name.
• Overwriting Existing Files: If a file with your custom name already exists in the destination folder, wget will overwrite it without warning.
• Handling Multiple URLs: If you pass multiple URLs to a single wget command while using the -O option, wget will concatenate all the downloaded contents into that single file. For downloading multiple files with unique names, it is best to run separate commands or use a script loop.