anew – append new lines to files without duplicates

anew is a command-line utility for adding lines to a file while avoiding duplicate entries.

The program reads records from standard input and checks whether they already appear in the destination file. New entries are appended, while records that have already been encountered are skipped.

By default, newly added lines are also printed to standard output. This makes the utility similar to tee in append mode, but with duplicate detection.

anew is useful for maintaining lists that receive regular additions, particularly when combining command output or collecting records from multiple sources.

The program includes options for checking which records would be added without modifying the destination and for suppressing standard output when only the file update is required.

This is free and open source software.

Key Features

• Appends only previously unseen lines to an existing file.
• Checks incoming records against lines already present in the destination.
• Prints newly added lines to standard output.
• Dry-run mode (-d) reports new lines without changing the destination file.
• Quiet mode (-q) appends records without printing them to standard output.
• Supports shell pipelines for filtering and collecting command output.
• Newly added records can be redirected to a separate file for further processing.

Website: github.com/tomnomnom/anew
Support:
Developer: Tom Hudson
License: MIT License

anew is written in Go. Learn Go with our recommended free books and free tutorials.

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