gunzip

What it does

gunzip decompresses files created by gzip, restoring the original file from its .gz counterpart. It's the direct inverse of gzip — where gzip file produces file.gz and removes file, gunzip file.gz produces file and removes file.gz. Internally gunzip is just gzip invoked in decompress mode, so every gzip option that makes sense in reverse (keep original, write to stdout, verbose, test) is available.

Beginner examples

• gunzip file.gz — decompress file.gz into file, removing the .gz file
• gunzip -k file.gz — decompress but keep file.gz around too
• gunzip -v file.gz — decompress with a verbose compression-ratio report
• gunzip file1.gz file2.gz file3.gz — decompress several files in one command

gunzip -k access.log.gz

Advanced examples

• Decompress to stdout and feed straight into another command without touching disk: gunzip -c dump.sql.gz | mysql mydb
• Recursively decompress every .gz file in a directory tree: gunzip -r ./archived-logs/
• Verify a batch of downloaded compressed files aren't corrupted before processing: gunzip -t *.gz
• List size and compression ratio for a directory of compressed files without decompressing any of them: gunzip -l *.gz

gunzip -c nightly-backup.sql.gz | psql mydb

Common mistakes

• Running gunzip file.gz and being surprised the .gz file disappeared — that's expected behavior; use -k if you need to keep it.
• Trying to gunzip a .tar.gz and expecting the tarball to also be extracted — gunzip only handles the gzip layer, leaving you with a plain .tar file that still needs tar -xf.
• Attempting to decompress a file that isn't actually gzip-formatted (e.g., renamed .zip to .gz) and getting a cryptic "not in gzip format" error.
• Running out of disk space because both the compressed and decompressed copies exist simultaneously — check available space with df -h first for large files.

Tips

• Use gunzip -l to preview compression ratio and size before committing to a full decompress, especially for files of unknown origin.
• gunzip -t is a cheap way to validate downloaded .gz files in a CI pipeline before relying on them.
• Remember gzip -d and gunzip are interchangeable — pick whichever reads better in a given script for clarity.

Best practices

• Prefer -k when decompressing files you might need to re-share or re-verify later, rather than relying on re-compressing afterward (which can produce a slightly different byte-for-byte file).
• In automated pipelines, always check gunzip's exit status (or pair with -t first) so a truncated download doesn't silently produce a partial, corrupted output file.
• When only one command downstream needs the data, stream via -c instead of writing an intermediate decompressed file to disk.

Real-world use cases

• Restoring a .gz-compressed database dump before importing it: gunzip -c dump.sql.gz | mysql dbname.
• Decompressing downloaded software distributions or datasets that are shipped as .tar.gz (as the first stage before tar -xf).
• Batch-decompressing a directory of rotated, compressed log files for a log-analysis tool that doesn't support reading .gz natively.

Common interview questions

• What's the difference between gunzip and gzip -d? None — they're the same operation; gunzip is effectively an alias/wrapper for gzip in decompress mode.
• How do you decompress a file without deleting the compressed original? gunzip -k file.gz.
• How would you fully extract a .tar.gz archive? Either gunzip file.tar.gz followed by tar -xf file.tar, or more directly in one step with tar -xzf file.tar.gz.