gzip Command: Tutorial & Examples

Compress or decompress files using the GNU zip algorithm

The gzip command is a widely used Linux utility for compressing and decompressing files using the GNU zip compression algorithm. It reduces file size to save disk space and speed up file transfers, making it an essential tool for system administrators and developers working on Linux servers. Typically used in combination with the tar command for archiving, gzip is a standard part of most Linux distributions.

How gzip Works

The gzip command compresses files by applying the DEFLATE algorithm, which combines LZ77 compression and Huffman coding to reduce file size without losing data (lossless compression). When you compress a file with gzip, it replaces the original file with a compressed version, appending the .gz extension. Decompression restores the original file exactly.

The compression level can be adjusted from -1 (fastest, least compression) to -9 (slowest, maximum compression), allowing users to balance speed and file size.

What gzip Does

Compresses one or more files, replacing them with .gz versions by default.
Decompresses .gz files, restoring the original files.
Supports listing compressed file details.
Can output decompressed data to standard output without creating files.
Integrates with other tools like tar to create compressed archives.

Why gzip Is Important

On Linux servers, saving disk space and reducing network bandwidth are critical. gzip is a simple, reliable tool to compress log files, backups, and data transfers. Its ubiquity and compatibility make it a universal choice for file compression. While newer algorithms exist, gzip remains widely supported and often faster to decompress, which is important for server performance.

Common Command Line Options

-d: Decompress the specified file(s). Equivalent to the gunzip command.
-k: Keep the original file(s) after compression or decompression.
-c: Write output to standard output (stdout) and do not remove original files.
-v: Verbose mode; display compression ratio and file size details.
-l: List compressed file contents with size details.
-1 to -9: Set compression level (-1 fastest, least compression; -9 slowest, maximum compression).
-r: Recursively compress files in directories.
--fast: Equivalent to -1.
--best: Equivalent to -9.

Basic Usage Examples

gzip file.txt

Compresses file.txt and replaces it with file.txt.gz. The original file is deleted by default.

gzip -d file.txt.gz

Decompresses file.txt.gz and restores file.txt.

gunzip file.txt.gz

Equivalent to gzip -d.

gzip -k file.txt

Compresses file.txt but keeps the original file intact.

gzip -c file.txt > file.txt.gz

Compresses file.txt and writes output to file.txt.gz without deleting the original file.

gzip -v file.txt

Compresses file.txt and shows compression details.

Typical output:

file.txt:     45.2% -- replaced with file.txt.gz

gzip -l file.txt.gz

Lists compressed file details:

compressed        uncompressed  ratio uncompressed_name
1234              2830          56.4% file.txt

Advanced Usage Examples

Compressing Multiple Files Recursively

gzip -r /var/log

Compresses all files under /var/log recursively.

Using gzip With tar

Create a compressed archive of a directory:

tar -czf backup.tar.gz /etc

Extract a compressed archive:

tar -xzf backup.tar.gz

Viewing Compressed File Contents Without Decompressing

zcat file.txt.gz

Prints the decompressed contents of file.txt.gz to stdout.

Using Different Compression Levels

gzip -9 largefile

Compress largefile with maximum compression.

gzip -1 largefile

Compress largefile quickly with less compression.

Common Errors and Troubleshooting

Permission Denied: Occurs if you lack write permissions on the file or directory.

Fix: Use sudo or adjust file permissions.
File Not Found: Happens if the specified file does not exist.

Check filenames or paths for typos.
Disk Full: Compression may fail if the disk is full.

Free up space or choose a different output location.
Corrupted gzip File: Decompression errors can indicate file corruption.

Verify file integrity or restore from backup.

Performance Considerations

Higher compression levels (-9) increase CPU usage and time but reduce file size.
Lower levels (-1) compress faster but produce larger files.
gzip is generally faster at decompression than compression.
For very large files or high-performance needs, consider alternatives like zstd.

Security Considerations

Avoid decompressing untrusted .gz files to prevent potential exploits or decompression bombs.
Use secure permissions when compressing sensitive files.
gzip does not encrypt data; use additional tools like gpg for encryption.

Alternatives and Related Commands

gunzip: Decompress gzip files; equivalent to gzip -d.
zcat: View contents of compressed files without decompressing.
tar: Archiving utility often combined with gzip for .tar.gz files.
zstd: Modern compression tool offering higher speed and compression.
bzip2: Alternative compression with better compression ratio but slower.

Tips and Best Practices

Use gzip -v to monitor compression progress.
Keep original files with -k if you want to retain uncompressed copies.
Combine gzip with tar for archiving directories.
Use appropriate compression level for your use case considering speed vs size.
Regularly compress old log files to save disk space.
Avoid compressing already compressed files (e.g., .zip, .jpg) as it wastes CPU.

Recommendation: zstd

While gzip is a great tool for compressing files, we recommend using zstd for even better compression and decompression speeds. It's a powerful compression algorithm, particularly useful for large files.