When working with file archiving using tar
, it’s common to exclude certain files or directories. However, understanding the total size of the included files can be a challenge. In this article, we’ll explore how to compute the total size of files included by tar
after applying exclude flags.
Understanding the Problem
The original challenge can be articulated as follows: How do you compute the total size of the files that are archived by tar
after excluding certain files using exclude flags?
Original Code Example
Here's a simple example of how you might use tar
with exclude flags:
tar -cvf archive.tar --exclude='*.tmp' --exclude='backup/' /path/to/source
In this command, we create an archive named archive.tar
, excluding all files with the .tmp
extension and the backup
directory within /path/to/source
.
Steps to Compute Total Size of Included Files
To calculate the size of files included in a tar
archive after excluding specified files, follow these steps:
-
List the Archive Contents: Use the
tar -tf
command to list the contents of your archive. This will give you an overview of the files included.tar -tf archive.tar
-
Extract File Sizes: Combine the output from the previous command with the
wc
(word count) ordu
(disk usage) command to get the sizes of these files.To do this efficiently, you can use the following command pipeline:
tar -tf archive.tar | xargs -I {} du -ch {} | grep total$
Here,
du -ch
computes the total size in a human-readable format, andgrep total$
filters the output to show only the total size.
Analyzing the Output
- The
tar -tf
command lists every file that’s included in the archive after excluding the specified ones. - The
du
command calculates the size for each of these files. - The
grep
command extracts just the total size at the end, making the output clear and concise.
Example
Let’s say you have the following directory structure:
/path/to/source
├── file1.txt
├── file2.tmp
└── backup
└── file3.log
When you run the command:
tar -cvf archive.tar --exclude='*.tmp' --exclude='backup/' /path/to/source
You are including file1.txt
while excluding file2.tmp
and all contents within the backup
directory.
After running the pipeline to calculate sizes:
tar -tf archive.tar | xargs -I {} du -ch {} | grep total$
You would get output similar to:
10K total
This indicates that the total size of file1.txt
included in archive.tar
is 10K.
Additional Considerations
When using the above method, keep in mind:
- Special Files: If your archive contains special files (like device files),
du
may not provide accurate sizes. - Symbolic Links: The size of symbolic links may not represent the size of the target files.
- Performance: For large archives or directories, the process might take some time, and you might want to consider parallel processing techniques.
Useful Resources
- GNU Tar Manual: Detailed documentation on the
tar
command. - Linux Command Line Basics: A great introduction for beginners to understand Linux commands.
Conclusion
Computing the total size of files included in a tar
archive after applying exclude flags can be done efficiently with simple command-line tools. By leveraging tar
, du
, and grep
, you can easily obtain a clear understanding of the space your files occupy. Whether you are managing backups or compressing files for distribution, understanding these commands will enhance your command-line proficiency.
Feel free to experiment with the commands and modify them according to your specific needs for file archiving.