How to Append Wget Output to an Existing Log File?

When automated scripts or long-duration downloads are running, maintaining a continuous log of the standard output is crucial for troubleshooting. By default, using the standard redirection or specific wget logging flags can overwrite your previous log files, wiping out valuable historical data. This article provides a quick, actionable guide on how to safely append wget output to an existing file using both native command-line redirection operators and built-in wget flags.

Using Native Command-Line Redirection

The most common and shell-agnostic way to append output to a file is by using the standard shell redirection operator >>. By combining this with 2>&1, you ensure that both standard output (stdout) and standard error (stderr) are captured, since wget sends its progress and status updates to stderr.

wget -O- https://example.com/file.zip >> download.log 2>&1

In this command:

• -O- tells wget to output the downloaded file content to stdout (if you are trying to log the file content itself).
• >> download.log appends the stdout to your log file.
• 2>&1 redirects stderr to stdout, ensuring the download progress and connection logs are also appended.

If you want to save the downloaded file normally to your disk and only append the terminal progress log to a file, combine the normal command with the redirection operator:

wget https://example.com/file.zip >> download.log 2>&1

Using the Built-In Wget Append Flag

If you prefer to use wget’s native capabilities without relying on shell redirection, the utility features a dedicated flag designed specifically for appending logs. The -a (or --append-output) flag directs wget to write all of its status messages to the end of a specified file.

wget -a download.log https://example.com/file.zip

Key Differences to Remember

Choosing between these two methods depends on your specific workflow requirements:

• The -a flag is clean, easy to remember, and handles the internal redirection of wget’s progress automatically. It will create the file if it doesn’t exist, or append to it if it does.
• The >> operator is a universal shell feature. It is highly useful if you are chaining multiple different commands together in a bash script and want all of them to log to the exact same file sequentially.