Tar archiving that takes input from a list of files
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Tar Archiving from a File List: Advanced Linux Archiving Techniques
Learn how to efficiently create tar archives by providing a list of files as input, an essential technique for selective backups and complex archiving scenarios in Linux and Unix environments.
The tar utility is a cornerstone of archiving in Linux and Unix-like systems, widely used for bundling multiple files into a single archive file, often for backup or distribution. While tar is commonly used by specifying files directly on the command line, there are scenarios where you need to archive a specific set of files that are listed in a separate file. This article will guide you through the process of using tar with a list of files, covering practical examples and best practices.
Why Archive from a File List?
Archiving from a file list offers significant advantages in specific situations:
- Selective Archiving: When you need to archive a non-contiguous or highly specific set of files that would be cumbersome to list manually.
- Automation: For scripting backup processes where the list of files to be archived is generated dynamically.
- Handling Long File Paths: To bypass command-line length limitations when dealing with a large number of files or very long file paths.
- Consistency: Ensuring that the exact same set of files is archived every time, preventing accidental omissions or inclusions.
Process flow for archiving from a file list
Creating a File List
Before you can archive from a list, you need to create the list itself. This is typically a plain text file where each line contains the path to a file or directory you want to include in the archive. You can generate this list using various commands like find, ls, or by manually compiling it.
find /path/to/source -name "*.log" > files_to_archive.txt
find /path/to/project -type f -print > project_files.txt
ls -1 /path/to/backup_dir/*.conf > config_files.txt
Examples of generating file lists using find and ls
tar command, to avoid 'file not found' errors. Each path should be on a new line.Using tar with --files-from
The tar command provides the --files-from (or -T) option to read the list of files to be archived from a specified file. This is the core functionality we're focusing on. The syntax is straightforward.
tar -cvf my_archive.tar -T files_to_archive.txt
Archiving files listed in files_to_archive.txt into my_archive.tar
-c option creates a new archive, -v provides verbose output (showing files being added), and -f specifies the archive filename. Add -z for gzip compression or -j for bzip2 compression if needed (e.g., tar -czvf my_archive.tar.gz -T files_to_archive.txt).Advanced Scenarios and Considerations
When working with file lists, you might encounter more complex requirements or need to handle specific edge cases.
Excluding Files from the List:
If your file list contains files you wish to exclude, tar provides the --exclude-from option. However, it's often simpler to filter your initial file list before passing it to tar.
grep -v "\.tmp$" files_to_archive.txt > filtered_files.txt
tar -cvf my_archive.tar -T filtered_files.txt
Using grep to exclude temporary files from the list
Handling Special Characters and Spaces:
If your file paths contain spaces or other special characters, it's crucial to ensure your file list handles them correctly. By default, tar expects one file per line. If you're generating the list with find, using the -print0 option and combining it with xargs -0 for tar is the safest approach, though tar -T generally handles spaces in filenames well if they are properly quoted or not split across lines.
find . -type f -print0 > files_with_spaces.txt
tar -cvf my_archive.tar --null -T files_with_spaces.txt
Using --null with -T to handle null-terminated filenames from find -print0
Practical Steps: Archiving Project Files
Let's walk through a common scenario: archiving specific configuration files and source code from a project directory.
1. Step 1
Navigate to your project root directory: cd /path/to/your/project
2. Step 2
Generate a list of files to include. For instance, all .conf files and .js files in the src directory: find . -name "*.conf" -o -name "*.js" > project_files.txt
3. Step 3
Inspect the generated project_files.txt to ensure it contains the correct paths.
4. Step 4
Create the tar archive using the file list: tar -czvf project_backup.tar.gz -T project_files.txt
5. Step 5
Verify the contents of the created archive: tar -tf project_backup.tar.gz